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Full text of "A compendious system of anatomy : in six parts : part I : Osteology ; II. Of the muscles, &c. ; III. Of the abdomen ; IV. Of the thorax ; V. Of the brain and nerves ; VI. Of the senses ; from the Encyclopaedia : illustrated with twelve large copperplates"



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\**M » i#r<frft' ^ 







SYSTEM 



O F 



ANATOMY. 



^ 



COMPENDIOUS SYSTEM 



O F 



ANATOMY. 



IN SIX PARTS. 



I. OSTEOLOGY. 

II. OF THE MUSCLES, &C. 
HI. OF THE ABDOMEN. 



IV. OF THE THORAX. 

V. OF THE BRAIN AND NERVES. 

VI. OF THE SENSES, 



FROM THE ENCYCLOPEDIA. 



Illustrated ivith Twelve large Copperplates 




PHILADELPHIA : 



PRINTED BY ARCHIBALD BARTRAM, 
FOR THOMAS DOBSON, AT THE STONE HOUSE, No. 41, 
SOUTH SECOND-STREET. 



1805. 



. t>? .•«*!£ 



CONTENTS. 

Page. 

Introduction 9 

1. History of anatomy ibid. 

2. View of the subject in general, and 
plan of the following treatise 40 

Part I. Osteology 57 
Sect. I. Of the bones in general, with their 

appendages, &c. 58 

II. Of the bones of the head 7 1 

1. Bones of the cranium and face 72 

2. Proper bones of the face 8 5 

3. Of the teeth 9 1 

4. os hyoides 98 
III. bones of the trunk 99 

1. spine ibid. 

2. bones of the thorax 108 

3. bones of the pelvis ill 
J^". Extremities 114 

1. upper extremities 115 

1. shoulder ibid. 

2. fo/jfs of the arm 117 

3. £ow£\s of the hand 121 
2. lower extremities 124 

1. fAig-^ ibid. 

2. rotula, or hiee-pan 126 

3. &£ 127 



( vi ) 

Page 

4. Of the foot 129 

4. oss a sesamoidea 133 

Explanationof the plates of osteology 134, 152 

Part II. Of the Soft Parts in general 157 

Of the common integuments, with their 

appendages ; and of the muscles ibid. 

Sec. I. Of the skin IS 9 

1. scarf-skin ibid. 

2. rete mucosum 160 

3. cutis, or true skin 161 

4. glands of the skin 162 

5 . insensible perspiration and 

sweat 163 

6. nails 166 

7. /jair 167 

8. cellular membrane and fat 168 
ZZ". muscles 170 

particular muscles 180 

J ta£/<? o/7/je muscles arranged according 

to their situation 1 8 1 

Explanation of plates XXIII. XXIV. 230,233 

Part III. Of the Abdomen, or Low- 
er Belly. 236 
Sec, I. Of the peritoneum 238 
II. omentum 239 



( vii ) 

Page 

Sec. III. Of the stomach 241 

IV. oesophagus 243 

P. intestines 244 

VI. mesentery 248 

.VII. pancreas 251 

VIII. liver 253 

IX. gall-bladder 25 5 

X. spleen 258 
XL glandule reflates, kidneys 

and ureters 259 

XII urinary bladder 262 

XIII Of digestion 266 

XIV. Of the course of the chyle and of 

the lymphatic system 278 

XV. Of the generative organs ; of 

conception, &c. 284 

1. The male orgatis ibid. 

2. Female organs of generation 296 

3. Of conception 501 

4. 0/* f/ze* fcetus in titer o 304 
Explanation of plates XXV. XXVI. 

and XXVII. 309, 316 

Part IV. Of the Thorax 318 

Sec. I. Of the breasts 319 

II. pleura 320 

III. thymus 322 

IV. diaphragm ibid. 

V. trachea 324 



( viii ) 

Page 

Sec. VI. Of the lungs 327 

VII Of respiration 329 

VIII Of the voice 334 

IX. Of dejection 336 

X. Of the pericardium, and of the 

heart, and its auricles 337 

XI. Angiology, or a description of 

the blood-vessels 342 

XII Of the action of the heart, 

auricles, and arteries 352 

XIII. Of the circulation 354 

XIV. nature of the blood 355 

XV. Of nutrition 357 
X VI. Of the glands and secretions 359 

Explanation of plate XXVIII. S64 

Part V. Of the Brain and Nerves 366 

Sec. I. Of the brain and its integuments ibid. 

II nerves 379 

Explanation of plate XXIX. 386 

Part VI. Of the Senses and their 



Organs 


390 


. I. Of touch 


ibid. 


II. taste 


391 


III. smelling 


393 


IV. hearing 


396 


V. vision 


404 


blanation of plate XXX. 


415 



SYSTEM 



OF 



ANATOMY. 



ANATOMY, 



THE art of dissecting, or artificially separat- 
ing and taking to pieces, the different 
parts of the human body, in order to an exact 
discoveiy of their situation, structure, and (eco- 
nomy. — The word is Greek, ««T V »i derived from 
«v«T«/xv<i>, to dissect, or separate by cutting. 

INTRODUCTION. 

1. History of Anatomy. 

This art seems to have been very ancient ; 
though, for a long time, known only in an im- 
perfect manner. — The first men who lived 
must have soon acquired some notions of the 
structure of their own bodies, particularly of 
the external parts, and of some even of the 
internal, such as bones, joints, and sinews, 
which are exposed to the examination of the 
senses in living bodies. 

B 



10 History of Anatomy. 

This rude knowledge must have been gra- 
dually improved, by the accidents to which 
the body is exposed, by the necessities of life, 
and by the various customs, ceremonies, and 
superstitions, of different nations. Thus, the 
observance of bodies killed by violence, at- 
tention to wounded men, and to many diseases, 
the various ways of putting criminals to death, 
the funeral ceremonies, and a variety of such 
things, must have shown men every day more 
and more of themselves ; especially as curio- 
sity and self-love would here urge them pow- 
erfully to observation and reflection. 

The brute-creation having such an affinity 
to man in outward form, motions, senses, and 
ways of life ; the generation of the species, 
and the effect of death upon the body, be- 
ing observed to be so nearly the same in both ; 
the conclusion was not only obvious, but un- 
avoidable, that their bodies were formed near- 
ly upon the same model. And the opportu- 
nities of examining the bodies of brutes were 
so easily procured, indeed so necessarily oc- 
curred m the common business of life, that 
the huntsman in making use of his prey, the 
priest in sacrificing, the augur in divination, 
and, above all, the butcher, or those who might 
out of curiosity attend upon his operations, 
must have been daily adding to the little stock 
of anatomical knowledge. Accordingly we 
find, in fact, that the South-sea islanders, who 
have been left to their own observation and 
reasoning, without the assistance of letters, 
have yet a considerable share of rude or wild 



History of Anatomy. 1 1 

anatomical and physiological knowledge. Dr. 
Hunter informs us, that when Omai was in 
his museum with Mr. Banks, though he could 
not explain himself intelligibly, they plainly 
saw that he knew the principal parts of the bo- 
dy, and something likewise of their uses ; and 
manifested a great curiosity or desire of hav- 
ing the functions of the internal parts of the 
body explained to him, particularly the relative 
functions of the two sexes, which with him 
seemed to be the most interesting object of 
the human mind. 

We may further imagine, that the philoso- 
phers of the most early ages, that is, the men 
of curiosity, observation, experience and re- 
flection, could not overlook an instance of na- 
tural organization, which was so interesting, 
and at the same time so wonderful, more es- 
pecially such of them as applied to the study 
and cure of diseases. We know that physic 
was a branch of philosophy till the age of 
Hippocrates. 

Thus the art must have been circumstanced 
in its beginning. We shall next see from the 
testimony of historians and other writers, 
how it actually appeared as an art, from the 
time that writing was introduced among men ; 
how it was improved and conveyed down to us 
through a long series of ages. 

Civilization and improvements of every kind, 
would naturally begin in fertile countries and 
healthful climates, where there would be lei- 
sure for reflection, and an appetite for amuse- 
ment. Accordingly, writing, and many other 



12 History of Anatomy. 

useful and ornamental inventions and arts, ap- 
pear to have been cultivated in the eastern parts 
of Asia long before the earliest times that are 
treated of by the Greek or other European wri- 
ters ; and that the arts and learning of those 
eastern people were in subsequent times gra- 
dually communicated to adjacent countries, es- 
pecially by the medium of traffic. The cus- 
toms, superstitions, and climate of eastern coun- 
tries, however, appear to have been as unfa- 
vourable to practical anatomy, as they were 
inviting to the study of astronomy, geometry, 
poetry, and all the softer arts of peace. 

Animal bodies there, run so quickly into 
nauseous putrefaction, that the early inha- 
bitants must have avoided such offensive em- 
ployments, as anatomical inquiries, like their 
posterity at this day. And, in fact, it does 
not appear, by the writings of the Greci- 
ans, or Jews, or Phoenicians, or of other eas- 
tern countries, that anatomy was particularly 
cultivated by any of those eastern nations. In 
tracing it backwards to its infancy, we cannot 
go farther into antiquity than the times of the 
Grecian philosophers. As an art in the state 
of some cultivation, it may be said to have 
been brought forth and bred up among them 
as a branch of natural knowledge. 

The asra of philosophy, as it was called, 
began with Thales the Milesian being declar- 
ed by a very general consent of the people, 
the most wise of all the Grecians, 480 years be- 
fore Christ. The philosophers of his school, 
which was called the Ionian, cultivated prin- 



History of Anatomy. 13 

oipally natural knowledge. Socrates, the se- 
venth in succession of their great teachers, in- 
troduced the study of morals, and was thence 
said to bring down philosophy from heaven, 
to make men truly wise and happy. 

In the writings of his scholar and successor 
Plato, we see that the philosophers had care- 
fully considered the human body, both in its 
organization and functions ; and though they 
had not arrived at the knowledge of the more 
minute and intricate parts, which required 
the successive labour and attention of many 
ages, they had made up very noble and com- 
prehensive ideas of the subject in general. 
The anatomical descriptions of Xenophon and 
Plato have had the honour of being quoted 
by Longinus ($xxxii.) as specimens of sub- 
lime writing ; and the extract from Plato is 
still more remarkable for its containing the 
rudiments of the circulation of the blood. "The 
heart (says Plato) is the centre or knot of the 
blood-vessels ; the spring or fountain of the 
blood which is carried impetuously round ; the 
blood is the pabulum or food of the flesh ; 
and, for the purpose of nourishment, the body 
is laid out into canals, like those which are 
drawn through gardens, that the blood may 
be conveyed, as from a fountain, to every 
part of the pervious body." 

Hippocrates was nearly contemporary with 
the great philosophers of whom we have been 
speaking, about 400 years before the Christi- 
an ajra. He is said to have separated the pro- 
fession of philosophy and physic, and to have 



14 History of Anatomy. 

been the first who applied to physic alone as 
the business of his life. He is likewise gene- 
rally supposed to be the first who wrote upon 
anatomy. We know of nothing that was writ- 
ten expressly upon the subject before; and 
the first anatomical dissection which has been 
recorded, was made by his friend Democritus 
of Abdera. 

If, however, we read the works of Hippo- 
crates with impartiality, and apply his ac- 
counts of the parts to what we now know of 
the human body, we must allow his descrip- 
tions to be imperfect, incorrect, sometimes ex- 
travagant, and often unintelligible, that of the 
bones only excepted. He seems to have stu- 
died these with more success than the other 
parts, and tells us that he had an opportunity 
of seeing an human skeleton. 

From Hippocrates to Galen, who flourish- 
ed towards the end of the second century, in 
the decline of the Roman empire, that is, in 
the space of 600 years, anatomy was greatly 
improved ; the philosophers still considering 
it as a most curious and interesting branch of 
natural knowledge, and the physicians, as a 
principal foundation of their art. Both of 
them, in that interval of time, contributed dai- 
ly to the common stock, by more accurate and 
extended observations, and by the lights of 
improving philosophy. 

As these two great men had applied very 
particularly to the study of animal bodies, 
they not only made great improvements* es- 
pecially in physiology, but raised the credit 



History of Anatomy. 15 

of natural knowledge, and spread it as wide 
as Alexander's empire. 

Few of Aristotle's writings were made pub- 
lic in his lifetime. He affected to say that 
they would be unintelligible to those who 
had not heard them explained at his lectures : 
and, except the use which Theophrastus made 
of them, they were lost to the public for above 
130 years after the death of Theophrastus; 
and at last came out defective from bad pre- 
servation, and corrupted by men, who, with- 
out proper qualifications, presumed to correct 
and supply what was lost. 

From the time of Theophrastus, the study 
of natural knowledge at Athens was for ever 
on the decline ; and the reputation of the Ly- 
cseum and Academy was almost confined to 
the studies which are subservient to orato- 
ry and public speaking. 

The other great institution for Grecian edu- 
cation, was at Alexandria in Egypt. The first 
Ptolemies, both from their love of literature, 
and to give true and permanent dignity to their 
empire, and to Alexander's favourite city, set 
up a grand school in the palace itself, with 
a museum and library, which, we may say, 
has been the most famed in the world. An- 
atomy, among other sciences, was publicly 
taught ; and the two distinguished anatomists 
were Erasistratus the pupil and friend of The- 
ophrastus, and Herophilus. Their volumi- 
nous works are all lost ; but they are quoted 
by Galen almost in every page. These pro- 
fessors were probably the first who were au- 



16 History of Anatomy. 

thorised to dissect human bodies ; a peculiari- 
ty which marks strongly the philosophical 
magnanimity of the first Ptolemy, and fixes 
a great sera in the history of anatomy. And it 
was, no doubt, from this particular advantage 
which the Alexandrians had above all others, 
that their school not only gained, but for ma- 
ny centuries preserved, the first reputation 
for medical education. Ammianus Marcelli- 
nus, who lived about 650 years after the ' 
Schools were set up, says, they were so fa- 
mous in his time, that it was enough to se- 
cure credit to any physician, if he could say 
he had studied at Alexandria. 

Herophilus has been said to have anato- 
mized 700 bodies. We must allow for exagge- 
ration. Nay, it was said, that both he and 
Erasistratus made it a common practice to 
open living bodies, that they might discover 
the more secret springs of life. But this, no 
doubt was only a vulgar opinion, rising from 
the prejudices of mankind; and accordingly, 
without any good reason, such tales have 
been told of modern anatomists, and have been 
believed by the vulgar. 

Among the Romans, though it is pro- 
bable they had physicians and surgeons from 
the foundation of the city, yet we have no 
account of any of these applying themselves 
to anatomy for a very long time. Archagathus 
was the first Greek physician established in 
Rome, and he was banished the city on ac- 
count of the severity of his operations. — 
Asclepiades, who flourished in Rome 101 



History of Anatomy* 11 

years after Archagathus, in the time of Pom- 
pey, attained such a high reputation as to be 
ranked in the same class with Hippocrates. 
He seemed to have some notion of the air in 
respiration acting by its weight ; and in ac- 
counting for digestion, he supposed the food 
to be no farther changed than by a comminu- 
tion into extremely small parts, which being 
distributed to the several parts of the body, 
is assimilated to the nature of each. One 
Cassius, commonly thought to be a disciple 
of Asclepiades, accounted for the right side 
of the body becoming paralytic on hurting the 
left side of the brain, in the same manner as 
has been done by the moderns, viz. by the 
crossing of the nerves from the right to the left 
side of the brain. 

From the time of Asclepiades to the second 
century, physicians seem to have been great- 
ly encouraged at Rome ; and, in the writings of 
Celsus, Rufus, Pliny, Ccelius, Aurelianus, 
and Arseteus, we find several anatomical ob- 
servations, but mostly very superficial and 
inaccurate. Towards the end of the second 
century lived Claudius Gallenus Pergamus, 
whose name is so well known in the medical 
world. He applied himself particularly to the 
study of anatomy, and did more in that way 
than all that went before him. He seems, 
however, to have been at a great loss for hu- 
man subjects to operate upon; and therefore 
his descriptions of the parts are mostly taken 
from brute animals. His works contain the 
fullest history of anatomists, and the most 

C 



18 History of Anatomy. 

complete system of the science, to be met 
with any where before him, or for several 
centuries after; so that a number of passages 
in them were reckoned absolutely unintelligible 
for many ages, until explained by the disco- 
veries of succeeding anatomists. 

About the end of the fourth century, Ni- 
mesius bishop of Emissa wrote a treatise on 
the nature of man, in which it is said were 
contained two celebrated modern discoveries ; 
the one, the uses of the bile, boasted of by 
Sylvius de la Boe ; and the other, the circula- 
tion of the blood. This last, however, is 
proved by Dr. Friend, in his history of phy- 
sic, p. 229. to be falsely ascribed to this au- 
thor. 

The Roman empire beginning now to be 
oppressed by the barbarians, and sunk in 
gross superstition, learning of all kinds de- 
creased ; and when the empire was totally 
overwhelmed by those barbarous nations, eve- 
ry appearance of science was almost extin- 
guished in Europe. The only remains of it 
were among the Arabians in Spain and in 
Asia. — The Saracens who came into Spain, 
destroyed at first all the Greek books which 
the Vandals had spared : but though their 
government was in a constant struggle and 
fluctuation during 800 years before they 
were driven out, they received a taste for 
learning from their countrymen of the east ; 
several of their princes encouraged liberal stu- 
dies ; public schools were set up at Cordova, 
Toledo, and other towns, and translations of 



History of Anatomy. 19 

the Greeks into the Arabic were universally in 
the hands of their teachers. 

Thus was the learning of the Grecians trans- 
ferred to the Arabians. But though they had 
so good a foundation to build upon, this art 
was never improved while they were masters 
of the world : for they were satisfied with 
commenting upon Galen ; and seem to have 
made no dissection of human bodies. 

Abdollaliph, who was himself a teacher of 
anatomy, a man eminent in his time (at and 
before 1203) for his learning and curiosity ; a 
great traveller, who had been bred at Bagdad, 
and had seen many of the great cities and 
principal places for study in the Saracen em- 
pire ; who had a favourable opinion of origin- 
al observation, in opposition to book-learning ; 
who boldly corrected some of Galen's errors, 
and was persuaded that many more might be 
detected ; this man, we say, never made or 
saw, or seemed to think of a human dissec- 
tion. He discovered Galen's errors in the oste- 
ology, by going to burying-grounds, with his 
students and others, where he examined and 
demonstrated the bones ; he earnestly recom- 
mended that method of study, in preference 
even to the reading of Galen, and thought that 
many farther improvements might be made ; 
yet he seemed not to have an idea that a fresh 
subject might be dissected with that view. 

Perhaps the Jewish tenets, which the Ma- 
hometans adopted, about uncleanliness and 
pollution, might prevent their handling dead 
bodies ; or their opinion of what was suppos- 



20 History of Anatomy. 

eel to pass between an angel and the dead 
person, might make them think disturbing the 
dead highly sacrilegious. Such, however, as 
Arabian learning was, for many ages together 
there was hardly any other in all the western 
countries of Europe. It was introduced by 
the establishment of the Saracens in Spain 
in 711, and kept its ground till the restora- 
tion of learning in the end of the 15th centu- 
ry. The state of anatomy in Europe, in the 
times of Arabian influence, may be seen by 
reading a very short system of anatomy drawn 
up by Mundinus, in the year 1315. It was 
extracted principally from what the Arabians 
had preserved of Galen's doctrine ; and, rude 
as it is, in that age, it was judged to be so 
masterly a performance, that it was ordered 
by a public decree, that it should be read in all 
the schools of Italy ; and it actually continu- 
ed to be almost the only book which was 
read upon the subject for above 200 years. 
Cortesius gives him the credit of being the 
great restorer of anatomy, and the first who 
dissected human bodies among the moderns. 

A general prejudice against dissection, how- 
ever, prevailed till the 16th century. The 
emperor Charles V. ordered a consultation to 
be held by the divines of Salamanca, in order 
to determine whether or not it was lawful in 
point of conscience to dissect a dead body. 
In Muscovy, till very lately, both anatomy 
and the use of skeletons were forbidden, the 
first as inhuman, and the latter as subservi- 
ent to witchcraft. 



History of 'Anatomy. 21 

In the beginning of the 1 5th century, learn- 
ing revived considerably in Europe, and par- 
ticularly physic, by means of copies of the 
Greek authors brought from the sack of Con- 
stantinople ; after which the number of anato- 
mists and anatomical books increased to a pro- 
digious degree. — The Europeans becoming 
thus possessed of the ancient Greek fathers 
of medicine, were for a long time so much 
occupied in correcting the copies they could 
obtain, studying the meaning, and comment- 
ing upon them, that they attempted nothing 
of their own, especially in anatomy. 

And here the late Dr. Hunter introduces 
into the annals of this art, a genius of the 
first rate, Leonardo da Vinci, who had been 
formerly overlooked, because he was of ano- 
ther profession, and because he published no- 
thing upon the subject. He is considered by 
the Doctor as by far the best anatomist and 
physiologist of his time ; and was certainly the 
first man we know of who introduced the prac- 
tice of making anatomical drawings. 

Vassere, in his lives of the painters, speaks 
of Leonardo thus, after telling us that he had 
composed a book of the anatomy of a horse, 
for his own study : " He afterwards applied 
himself with more diligence to the human an- 
atomy ; in which study he reciprocally receiv- 
ed and communicated assistance to Marc. An- 
tonio della Torre, an excellent philosopher, 
who then read lectures in Pavia, and wrote 
upon this subject ; and who was the first, as I 
have heard, who began to illustrate medicine 



22 History of Anatomy. 

from the doctrine of Galen, and to give true 
light to anatomy, which till that time had been 
involved in clouds of darkness and ignorance. 
In this he availed himself exceedingly of the 
genius and labour of Leonardo, who made a 
book of studies, drawn with red chalk, and 
touched with a pen, with great diligence, of 
such subjects as he had himself dissected ; 
where he made all the bones, and to those he 
joined, in their order, all the nerves, and co- 
vered them with the muscles. And concern- 
ing those, from part to part, he wrote remarks 
in letters of an ugly form, which are written 
by the left hand, backwards, and not to be un- 
derstood but by those who know the method 
of reading them ; for they are not to be read 
without a looking-glass. Of these papers of 
the human anatomy, there is a great part in 
the possession of M. Francesco da Melzo, a 
Milanese gentleman, who, in the time of Le- 
onardo, was a most beautiful boy, and much 
beloved by him, as he is now a beautiful and 
genteel old man, who reads those writings, 
and carefully preserves them, as precious re- 
licks, together with the portrait of Leonardo, 
of happy memory. It appears impossible that 
that divine spirit should reason so well upon 
the arteries, and muscles, and nerves, and 
veins ; and with such diligence of every thing, 
&c. &c." 

Those very drawings and the writings are 
happily found to be preserved in his Britan- 
nic Majesty's great collection of original draw- 
ings, where the Doctor was permitted to exa- 



History of Anatomy. 23 

mine them ; and his sentiments upon the oc- 
casion he thus expresses : u I expected to see 
little more than such designs in anatomy, as 
might be useful to a painter in his own pro- 
fession ; but I saw, and indeed with astonish- 
ment, that Leonardo had been a general and a 
deep student. When I consider what pains he 
has taken upon every part of the body, the su- 
periority of his universal genius, his particular 
excellence in mechanics and hydraulics, and 
the attention with which such a man would ex- 
amine and see objects which he was to draw, 
I am fully persuaded that Leonardo was the 
best anatomist at that time in the world. We 
must give the 15th century the credit of Leo- 
nardo's anatomical studies, as he was 55 years 
of age at the close of that century.'' 

In the beginning of the 16th century, Achil- 
linus and Benedictus, but particularly Beren- 
garius and Massa, followed out the improve* 
ment of anatomy in Italy, where they taught 
it, and published upon the subject. These 
first improvers made some discoveries from 
their own dissections : but it is not surprising 
that they should have been diffident of them- 
selves, and have followed Galen almost blind- 
ly, when his authority had been so long estab- 
lished, and when the enthusiasm for Greek 
authors was rising to such a pitch. 

Soon after this, we may say about the year 
1540, the great Vesalius appeared. He was 
studious, laborious, and ambitious. From 
Brussels, the place of his birth, he went to 
Louvain, and thence to Pans, where anatomy 



■> 



24 History of Anatomy. 

was not yet making a considerable figure, and 
then to Louvain to teach ; from which place, 
very fortunately for his reputation, he was call- 
ed to Italy, where he met with every oppor- 
tunity that such a genius for anatomy cbuld 
desire, that is, books, subjects, and excellent 
draughtsmen. He was equally laborious in 
reading the ancients, and in dissecting bodies. 
And in making the comparison, he could not 
but see, that there was great room for improve- 
ment, and that many of Galen's descriptions 
were erroneous. When he was but a young 
man, he published a noble system of anatomy, 
illustrated with a great number of elegant fi- 
gures. — In this work he found so many occa- 
sions of correcting Galen, that his contempo- 
raries, partial to antiquity, and jealous of his 
reputation, complained that he carried his turn 
for improvement and criticisms to licentious- 
ness. The spirit of opposition and emulation 
was presently roused ; and Sylvius in France, 
Columbus, Fallopius, and Eustachius in Italy, 
who were all in high anatomical reputation 
about the middle of this 16th century, endea- 
voured to defend Galen at the expense of Ve- 
salius. In their disputes they made their ap- 
peals to the human body: and thus in a few 
years the art was greatly improved. And Ve- 
salius being detected in the very fault which 
he condemned in Galen, to wit, describing 
from the dissections of brutes, and not of the 
human body, it exposed so fully that blunder 
of the older anatomists, that in succeeding 
times there has been little reason for such 



History of Anatomy. 25 

complaint. — Besides the above, he published 
several other anatomical treatises. He has 
been particularly serviceable by imposing 
names on the muscles, most of which are re- 
tained to this day. Formerly they were dis- 
tinguished by numbers, which were different- 
ly applied by almost every author. 

In 1561, Gabriel Fallopius, professor of 
anatomy at Padua, published a treatise of ana- 
tomy under the title of Observationes Anatomi- 
cal. This was designed as a supplement to 
Vesalius ; many of whose descriptions he cor- 
rects, though he always makes mention of him 
in an honourable manner. Fallopius made 
many great discoveries, and his book is well 
worth the perusal of every anatomist. 

In 1563, Bartholomseus Eustaehius pub- 
lished his Opuscala Anatomica at Venice, which 
have ever since been justly admired for the ex- 
actness of the descriptions, and the discove- 
ries contained in them. He published after- 
wards some other pieces, in which there is lit- 
tle of anatomy ; but never published the great 
work he had promised, which was to be adorn- 
ed with copperplates representing all the parts 
of the human body. These plates, after lying 
buried in an old cabinet for upwards of 150 
years, were at last discovered and published 
in the year 1714, by Lancisi the pope's phy- 
sician ; who added a short explicatory text, be- 
cause Eustachius's own writing could not be 
found. 

From this time the study of anatomy gradu- 
ally diffused itself over Europe ; insomuch that 

D 



26 History of Anatomy. 

for the last hundred years it has been daily im- ' 
proving by the labour of a number of profes- 
sed anatomists almost in every country of Eu- 
rope. 

We may form a judgment about the state of 
anatomy even in Italy, in the beginning of the 
17th century, from the information of Corte- 
sius. He had been professor of anatomy at 
Bologna, and was then professor of medicine 
at Massana; where, though he had a great 
desire to improve himself in the art, and to fi- 
nish a treatise which he had begun on practi- 
cal anatomy, in 24 years he could twice only 
procure an opportunity of dissecting a human 
body, and then it was with difficulties and in 
hurry ; whereas he had expected to have done 
so, he says, once every year, according to the 
custom in the famous academies oj Italy. 

In the very end of the 16th century, the 
great Harvey, as was the custom of the times, 
went to Italy to study medicine ; for Italy was 
still the favourite seat of the arts : And in the 
very beginning of the 17th century, soon after 
Harvey's return to England, his master in ana- 
tomy, Fabricius ab Aquapendente, published 
an account of the valves in the veins, which 
he had discovered many years before, and no 
doubt taught in his lectures when Harvey at- 
tended him. 

This discovery evidently affected the estab- 
lished doctrine of all ages, that the veins car- 
ried the blood from the liver to all parts of the 
body for nourishment. It set Harvey to work 
upon the use of the heart and vascular systems 



History of Anatomy. 27 

iii animals ; and in the course of some years 
he was so happy as to discover, and to prove 
beyond all possibility of doubt, the circulation 
of the blood. He taught his new doctrine in 
his lectures about the year 1616, and printed 
it in 1628. 

It was by far the most important step thai 
had been made in the knowledge of animal bo- 
dies in any age. It not only reflected useful 
lights upon what had been already found out 
in anatomy, but also pointed out the means of 
further investigation. And accordingly we see, 
that from Harvey to the present time, anato- 
my has been so much improved, that we may 
reasonably question if the ancients have been 
further outdone by the moderns in any other 
branch of knowledge. From one day to ano- 
ther there has been a constant succession of 
discoveries, relating either to the structure or 
functions of our body ; and new anatomical 
processes, bo,th of investigation and demon- 
stration, have been daily invented. Many 
parts of the body, which were not known in 
Harvey's time, have since then been brought 
to light : and of those which were known, the 
internal composition and functions remained 
unexplained ; and indeed must have remained 
unexplicable without the knowledge of the cir- 
culation. 

Harvey's doctrine at first met with conside- 
rable opposition ; but in the space of about 20 
years it was so generally and so warmly em- 
braced, that it was imagined every thing in 
physic would be explained. But time and ex- 



28 History of Anatomy. 

perience have taught us, that we still are, and 
probably must long continue to be, very igno- 
rant ; and that in the study of the human body, 
and of its diseases, there will always be an 
extensive field for the exercise of sagacity. 

After the discovery and knowledge of the 
circulation of the blood, the next question 
would naturally have been about the passage 
and route of the nutritious part of the food or 
chyle from the bowels to the blood-vessels : 
And, by good fortune, in a few years after 
Harvey had made his discovery, Asellius, an 
Italian physician, found out the lacteals, or 
vessels which carry the chyle from the intes- 
tines ; and printed his account of them, with 
coloured prints, in the year 1627, the very 
year before Harvey's book came out. 

For a number of years after these two pub- 
lications, the anatomists in all parts of Europe 
were daily opening living dogs, either to see 
the lacteals or to observe the phenomena of 
the circulation. In making an experiment of 
this kind, Pecquet in France was fortunate 
enough to discover the thoracic duct, or com- 
mon trunk of all the lacteals, which conveys 
the chyle into the subclavian vein. He print- 
ed his discovery in the year 1651. And now 
the lacteals having been traced from the intes- 
tines to the thoracic duct, and that duct having 
been traced to its termination in a blood-ves- 
sel, the passage of the chyle was completely 
made out. 

The same practice of opening living animals 
furnished occasions of discovering the lympha- 



History of Anatomy. 29 

tic vessels. This good fortune fell to the 
lot of Rudbec first, a young Swedish anato- 
mist ; and then to Thomas Bartholine, a Da- 
nish anatomist, who was the first who appear- 
ed in print upon the lymphatics. His book 
came out in the year 16 53, that is, two years 
after that of Pecquet. And then it was very evi- 
dent that they had been seen before by Dr. Hig- 
more and others, who had mistaken them for 
lacteals. But none of the anatomists of those 
times could make out the origin of the lym- 
phatics, and none of the physiologists could 
give a satisfactory account of their use. 

The circulation of the blood, and the pas- 
sage of the chyle having been satisfactorily 
traced out in full-grown animals, the anato- 
mists were naturally led next to consider how 
these animal processes were carried on in 
the child while in the womb of the mother. 
Accordingly the male and female organs, the 
appearances and contents of the pregnant ute- 
rus, the incubated egg^ and every phenome- 
non which could illustrate generation, became 
the favourite subject, for about 30 years, with 
the principal anatomists of Europe. 

Thus it would appear to have been in theo- 
ry : but Dr. Hunter believes, that in fact, as 
Harvey's master Fabricius laid the foundation 
for the discovery of the circulation of the 
blood by teaching him the valves of the veins, 
and thereby inviting him to consider that sub- 
ject ; so Fabricius by his lectures, and by his 
elegant work De formato fcetu, et de formatione 
ovi et pulli, probably made that likewise a fa- 



30 History of Anatomy. 

vourite subject with Dr. Harvey. But whe- 
ther he took up the subject of generation in 
consequence of his discovery of the circula- 
tion, or was led to it by his honoured master 
Fabricius, he spent a great deal of his time 
in the inquiry ; and published his observations 
in a book De generatione animalium, in the 
year 1651, that is, six years before his death. 

In a few years after this, Swammerdam, Van 
Horn, Steno, and De Graaf, excited great at- 
tention to the subject of generation, by their 
supposed discovery that the females of vivipa- 
rous animals have ovaria, that is, clusters of 
eg^s in their loins, like oviparous animals ; 
which, when impregnated by the male, are 
conveyed into the uterus; so that a child is 
produced from an egg as well as a chick ; with 
this difference, that one is hatched within, and 
the other without, the body of the mother. 

Malpighi, a great Italian genius, some time 
after, made considerable advances upon the 
subject of generation. He had the good for- 
tune to be the first who used magnifying glass- 
es with address in tracing the first appearances 
in the formation of animals. He likewise made 
many other observations and improvements in 
the minutia of anatomy by his microscopical la- 
bours, and by cultivating comparative anato- 
my. 

This distinguished anatomist gave the first 
public specimen of his abilities, by printing a 
dissertation on the lungs anno 1661 ; a period 
so remarkable for the study of nature, that it 
would be injustice to pass it without particular 
notice. 



History of Anatomy. 31 

At the same time flourished Laurentius 
Bellinus at Florence, and was the first who 
introduced mathematical reasoning in physic. 
In 1662, Simon Pauli published a treatise De 
albandis ossibus. He had long been admired 
for the white skeletons he prepared ; and at 
last discovered his method, which was by ex- 
posing the bones all winter to the weather. 

Johannes Swammerdam of Amsterdam also 
published some anatomical treatises ; but was 
most remarkable for his knowledge of pre- 
serving the parts of bodies entire for many 
years, by injecting their vessels. He also 
published a treatise on respiration; wherein 
he mentioned his having figures of all the 
parts of the body as big as the life, cut in 
copper, which he designed to publish, with a 
complete systems of anatomy. These, howe- 
ver, were never made public by Swammerdam; 
but, in 1683, Gothofridus Bidloo, professor 
of anatomy at Leyden, published a work en- 
titled Anatomia corporis humani, where all the 
parts were delineated in very large plates al- 
most as big as the life. Mr. Cowper, an Eng- 
lish surgeon, bought 300 copies of these fi- 
gures ; and in 1698, published them with an 
English text, quite different from Bidloo's La- 
tin one ; to which were added letters in Bid- 
loo's figures, and some few figures of Mr. 
Cowper's own. To this work Cowper's name 
was prefixed, without the least mention of Bid- 
loo, except on purpose to confute him. Bid- 
loo immediately published a very ill-natured 
pamphlet, c lied Gitlielmtis Cowpcrus citatus 



32 History of Anatomy. 

coram tribunali; appealing to the Royal Soci- 
ety, how far Cowper ought to be punished 
as a plagiary of the worst kind, and endea- 
vouring to prove him an ignorant deceitful 
fellow. Cowper answered him in his own 
style, in a pamphlet called his V indicia ; en- 
deavouring to prove, either that Bidloo did 
not understand his own tables, or that they 
were none of his. It was even alleged that 
those were the tables promised by Swam- 
merdam, and which Bidloo had got from his 
widow. This, however, appears to have been 
only an invidious surmise, there being un- 
questionable evidence that they were really 
the performance of Bidloo. 

Soon after, Isbrandus Diembroeck, profes- 
sor of anatomy at Utrecht, began to appear 
as an author. His work contained very little 
original ; but he was at great pains to collect 
from others whatever was valuable in their 
writings, and his system was the common 
standard among anatomical students for ma- 
ny years. 

About the same time, Antonius Liew r en- 
hoeck of Delft, improved considerably on 
Malpighi's use of microscopes. These two 
authors took up anatomy w r here others had 
dropt it ; and, by this new art, they brought 
a number of amazing things to light. They 
discovered the red globules of the blood ; 
they were enabled to see the actual circula- 
tion of the blood in the transparent parts of 
living animals, and could measure the velo- 
city of its motion; they discovered that the 



History of Anatomy. 33 

arteries and veins had no intermediate cells 
or spungy substance, as Harvey and all the 
preceding anatomists had supposed, but com- 
municated one with the other by a continua- 
tion of the same tube. 

Liewcnhoeck was in great fame likewise 
for his discovery of the animalcula in the se- 
men. Indeed there was scarcely a part of the 
body, solid or fluid, which escaped his examina- 
tion ; and he almost every where found, that 
what appeared to the naked eye to be rude un- 
digested matter, was in reality a beautiful and 
regular compound. 

After this period, Nuck added to our know- 
ledge of the absorbent system already men- 
tioned, by his injections of the lymphatic 
glands ; Ruysch, by his description of the 
valves of the lymphatic vessels; and Dr. 
Meckel, by his accurate account of the whole 
system, and by tracing those vessels in many 
parts where they had not before been de- 
scribed. 

Besides these authors, Drs. Hunter and 
Monro have called the attention of the pub- 
lic to this part of anatomy, in their contro- 
versy concerning the discovery of the office 
of the lymphatics. 

When the lymphatic vessels were first seen 
and traced into the thoracic duct, it was natu- 
ral for anatomists to suspect, that as the lac- 
teals absorbed from the cavity of the intes- 
tines, the lymphatics, which are similar in 
figure and structure, might possibly do the 
same office with respect to other parts of the 

E 



34 History of Anatomy. 

bod) T : and accordingly, Dr. Glisson, who 
wrote in 16 54, supposes these vessels arose 
from cavities, and that their use was to ab- 
sorb ; and Frederic Hoffman has very expli- 
citly laid down the doctrine of the lymphatic 
vessels being a system of absorbents. But 
anatomists in general have been of a contra- 
ry opinion ; for, from experiments, particular- 
ly such as were made by injections, they have 
been persuaded that the lymphatic vessels did 
not arise from cavities, and did not absorb, 
but were merely continuations from small ar- 
teries. The doctrine, therefore, that the lym- 
phatics, like the lacteals, were absorbents, as 
had been suggested by Glisson and by Hoff- 
man, has been revived by Dr. Hunter and Dr. 
Monro, who have controverted the experi- 
ments of their predecessors in anatomy, and 
have endeavoured to prove that the lympha- 
tic vessels are not continued from arteries, 
but are absorbents. 

To this doctrine, however, several objec- 
tions have been started, particularly by Hal- 
ler (Elem. Phys. 1. 24. $ 2, 3.) ; and it has 
been found, that before the doctrine of the 
lymphatics being a system of absorbents can 
be established, it must first be determined 
whether this system is to be found in other 
animals besides man and quadrupeds. Mr. 
Hewson claims the merit of having proved 
the affirmative of this question, by discover- 
ing the lymphatic system in birds, fish, and 
amphibious animals. See Phil. Trans, vol. 
lviii. and lxix. — And latterly, Mr. Cruikshank 



History of Anatomy. 35 

has traced the ramifications of that system in 
almost every part of the body ; and from his 
dissections, figures have been made and lately 
published to the world. To Mr. Sheldon also 
we are much indebted for his illustration of 
this system, which promises to give great sa- 
tisfaction, but of which only a part has yet 
been published. 

The gravid uterus is a subject likewise 
which has received considerable improve- 
ments, particularly relating to one very im- 
portant discovery ; viz. that the internal mem- 
brane of the uterus, which Dr. Hunter has 
named decidua, constitutes the exterior part 
of the secundines or after-birth, and separates 
from the rest of the uterus every time that a 
woman either bears a child or suffers a mis- 
carriage. This discovery includes another, to 
wit, that the placenta is partly made up of an 
excrescence or efflorescence from the uterus 
itself. 

These discoveries are of the utmost conse- 
quence, both in the physiological question 
about the connection between the mother and 
child, and likewise in explaining the phenome- 
na of births and abortions, as well as in re- 
gulating obstetrical practice. 

The anatomists of this century have im- 
proved anatomy, and have made the study of 
it much more easy, by giving us more correct 
as well as more numerous figures. It is amaz- 
ing to think of what has been done in that 
time. We have had four large folio books of 
figures of the bones, viz. Cheselden's, Albi- 



36 History of Anatomy. 

nus's, Sue's and Trew's. Of the muscles, we 
have had two large folios ; one from Cowper, 
which is elegant ; and one from Albinus, 
which, from the accuracy and labour of the 
work, we may suppose will never be outdone. 
Of the blood-vessels we have a large folio 
from Dr. Haller. We have had one upon 
the nerves from Dr. Meckel, and another by 
Dr. Monro junior. We have had Albinus's, 
Roederer's, Jenty's, and Hunter's works up- 
on the pregnant uterus ; Weitbrecht and Le- 
ber on the joints and fresh bones ; Soemer- 
ring on the brain ; Zin on the eye ; Cotunius, 
Meckel junior, he. on the ear ; Walterus on 
the nerves of the thorax and abdomen ; Dr. 
Monro on the bursas mucosae, he. 

It would be endless to mention the anato- 
mical figures that have been published in this 
century, of particular and smaller parts of the 
body, by Morgagni, Ruysch, Valsalva, Sanc- 
torini, Heister, Vater, Cant, Zimmerman, 
Walterus, and others. 

Those elegant plates of the brain, howe- 
ver, just published by M. Vicq. d'Azyr, must 
not pass without notice, especially as they 
form part of an universal system of anatomy 
and physiology, both human and comparative, 
proposed to be executed in the same splendid 
style. Upon the brain alone 19 folio plates 
are employed; of which several are coloured. 
The figures are delineated with accuracy and 
clearness ; but the colouring is rather beauti- 
ful than correct. Such parts of this work as 
may be published; cannot fail to be equally 



History of Anatomy. 37 

acceptable to the anatomist and the philoso- 
pher; but the entire design is apparently too 
extensive to be accomplished within the peri- 
od of a single life. In Great Britain, also, a 
very great anatomical work is carrying on by 
Andrew Bell, F. S. A. S. engraver to his 
Royal Highness the Prince of Wales, with 
the approbation of Dr. Monro, and under the 
inspection of his very ingenious assistant Mr. 
Fyfe. It is to compose a complete illustra- 
tion, both general and particular, of the hu- 
man body, by a selection from the best plates 
of all the greatest anatomists, as well foreign 
as British, exhibiting the latest discoveries in 
the science, and accompanied with copious ex-- 
planations. The whole number of plates 
mentioned in the Prospectus is 240, of which 
152 are already done ; all in royal folio, 

To the foreign treatises already mentioned 
may be added those recently published by 
Sabbatier and Plenck on anatomy in general. 
In Great-Britain, the writings of Keil, Doug- 
las, Cheselden, the first Monro, Winslow, 
&tc. are too well known to need description. 
The last of these used to be recommended as 
a standard for the students of anatomy: but 
it has of late given place to a more accu- 
rate and comprehensive system, in three vo- 
lumes, published by Mr. Elliot of Edinburgh, 
upon a plan approved of by Dr. Monro, 
and executed by Mr. Fyfe. Dr. Simmons of 
London has also obliged the world with an 
excellent system of anatomy; and another 
work, under the title of " Elements of Ana- 



38 History of Anatomy. 

tomy and the Animal Oeconomy:" in which 
the subjects are treated with uncommon ele- 
gance and perspicuity. 

In the latter part of the last century, ana- 
tomy made two great steps, by the invention 
of* injections, and the method of making what 
we commonly call preparations. These two 
modern arts have really been of infinite use 
to anatomy ; and besides have introduced an 
elegance into our administrations, which in 
former times could not have been supposed 
to be possible. They arose in Holland un- 
der Swammerdam and Ruysch, and after- 
wards in England under Cowper, St. Andre, 
and others, where they have been greatly im- 
proved. 

The anatomists of former ages had no other 
knowledge of the blood-vessels, than what 
they were able to collect from laborious dis- 
sections, and from examining the smaller 
branches of them, upon some lucky occa- 
sion, when they were found more than com- 
monly loaded with red blood. But filling 
the vascular system with a bright coloured 
wax, enables us to trace the large vessels 
with great ease, renders the smaller much 
more conspicuous, and makes thousands of 
the very minute ones visible, which from their 
delicacy, and the transparency of their natu- 
ral contents, are otherwise imperceptible. 

The modern art of corroding the fleshy 
parts with a menstruum, and of leaving the 
moulded wax entire, is so exceedingly useful, 
and at the same time so ornamental, that it 



History of Anatomy. 39 

does great honour to the ingenious inventor 
Dr. Nicholls. 

The wax-work art of the moderns might de- 
serve notice in any history of anatomy, if the 
masters in that way had not been so careless 
in their imitation. Many of the wax-figures 
are so tawdry with a show of unnatural co- 
lours, and so very incorrect in the circum- 
stances of figure, situation, and the like, that 
though they strike a vulgar eye with admira- 
tion, they must appear ridiculous to an ana- 
tomist. But those figures which are cast in 
wax, plaster, or lead, from the real subject, 
and which of late years have been frequently 
made, are, of course, very correct in all the 
principal parts, and may be considered as no 
insignificant acquisition to modern anatomy. 
The proper, or principal use of this art is, to 
preserve a very perfect likeness of such sub- 
jects as we but seldom can meet with, or can- 
not well preserve in a natural state ; a subject 
in pregnancy, for example. 

The modern improved methods of preserv- 
ing animal bodies, or parts of them, has been 
of the greatest service to anatomy ; especially 
in saving the time and labour of the anato- 
mist in the nicer dissections of the small 
parts of the body. For now, whatever he 
has prepared with care, he can preserve; and 
the object is ready to be seen at any time. 
And in the same manner he can preserve ana- 
tomical curiosities, or rarities of every kind ; 
such as, parts that are uncommonly formed ; 
parts that are diseased; the parts of the preg. 



40 Introduction to Anatomy. 

nant uterus and its contents. Large collec- 
tions of such curiosities, which modern ana- 
tomists are striving almost every where to 
procure, are of infinite service to the art, es- 
pecially in the hands of teachers. They give 
students clear ideas about many things which 
it is very essential to know, and yet which it 
is impossible that a teacher should be able to 
show otherwise, were he ever so well suppli- 
ed with fresh subjects. 



■uuasfiUBBi 



2. View of the Subject in general, and Plan of 
the following Treatise. 

THE etymology of the word anatomy, as 
above given, implies simply dissection; but by 
this term something more is usually under- 
stood. 

It is every day made use of to express a 
knowledge of the human body ; and a person 
who is said to understand anatomy, is sup- 
posed to be conversant with the structure and 
arrangement of the different solid parts of the 
body. 

It is commonly divided into Anatomy, pro- 
perly so called ; and Comparative Anatomy : 
the first of these is confined solely to the hu- 
man body ; the latter includes all animals > so 
far as a knowledge of their structure may tend 
to perfect our ideas of the human body. 



Introduction to Anatomy. 41 

The term anatomy may also have another 
and more extensive signification: it may be 
employed to express not only a knowledge of 
the structure and disposition of the parts but 
likewise of their oeconomy and use. Consider- 
ed in this light, it will seldom fail to excite the 
curiosity of people of taste, as a branch of 
philosophy ; since if it is pleasing to be ac- 
quainted with the structure of the body, it is 
certainly more so to discover all the springs 
which give life and motion to the machine, 
and to observe the admirable mechanism by 
which so many different functions are exe- 
cuted. 

Astronomy and anatomy, as Dr. Hunter, 
after Fontenelle, observes, are the studies 
which present us with the most striking view 
of the two greatest attributes of the Supreme 
Being. The first of these fills the mind with 
the idea of his immensity, in the largeness, 
distances, and number of the heavenly bodies ; 
the last, astonishes with his intelligence and 
art in the variety and delicacy of animal me- 
chanism. 

The human body has been commonly 
enough known by the name of microcosmus, 
or the little world ; as if it did not differ so 
much from the universal system of nature in 
the symmetry and number of its parts as in 
their size. 

Galen's excellent treatise De usu partium, 
was composed as a prose hymn to the Crea- 
tor ; and abounds with as irresistible proofs 
of a supreme Cause and governing Provi- 

F 



42 Introduction to Anatomy. 

dence, as we find in modern physico-theology. 
And Cicero dwells more on the structure and 
ceconomy of animals than on all the produc- 
tions of nature besides, when he wants to 
prove the existence of the gods from the or- 
der and beauty of the universe. He there 
takes a survey of the body of man in a most 
elegant synopsis of anatomy, and concludes 
thus : " Quibus rebus expositis, satis docuisse 
videor, hominis natura, quanto omnes anteiret 
animantes. Ex quo debet intelligi, nee figu- 
ram situmque membrorum, nee ingenii men- 
tisque vim talem effici potuisse fortuna." 

The satisfaction of mind which arises from 
the study of anatomy, and the influence which 
it must naturally have upon our minds as phi- 
losophers, cannot be better conveyed than by 
the following passage from the same author : 
" Quae contuens animus, accepit ab his cogni- 
tionem deorum, ex qua oritur pietas : cui con- 
juncta justitia est, reliquseque virtutes : ex 
quibus vita beata exsistit, par et similes deo- 
rum, nulla alia re nisi immortalitate, quae ni- 
hil ad bene vivendum pertinet, cedens cceles- 
tibus." 

It would be endless to quote the animated 
passages of this sort which are to be found in 
the physicians, philosophers, and theologists, 
who have considered the structure and func- 
tions of animals with a view towards the Cre- 
ator. It is a view which must strike one with 
a most awful conviction. Who can know and 
consider the thousand evident proofs of the as- 
tonishing art of the Creator, in forming and 



Introduction to Anatomy. 43 

sustaining an animal body such as ours, with- 
out feeling the most pleasant enthusiasm ? Can 
we seriously reflect upon this awful subject, 
without being almost lost in adoration ? with- 
out longing for another life after this, in which 
we may be gratified with the highest enjoy- 
ment, which our faculties and nature seem ca- 
pable of, the seeing and comprehending the 
whole plan of the Creator, in forming the uni- 
verse and in directing all its operations ? 

But the more immediate purposes of anato- 
my concern those who are to be the guardians 
of health, as this study is necessary to lay a 
foundation for all the branches of medicine. 
The more we know of our fabric, the more 
reason we have to believe, that if our senses 
were more acute, and our judgment more en- 
larged, we should be able to trace many 
springs of life which are now hidden from us : 
by the same sagacity we should discover the 
true causes and nature of diseases ; and there- 
by be enabled to restore the health of many, 
who are now, from our more confined know- 
ledge, said to labour under incurable disor- 
ders. By such an intimate acquaintance with 
the ceconomy of our bodies, we should disco- 
ver even the seeds of diseases, and destroy 
them before they had taken root in the consti- 
tution. 

That anatomy is the very basis of surgery 
every body allows. It is dissection alone that 
can teach us, where we may cut the living 
body with freedom and dispatch ; and where 
we may venture with great circumspection and 



L4 Introduction to Anatomy. 

delicacy ; and where we must not, upon any 
account, attempt it. This informs the head, 
gives dexterity to the hand, and familiarizes 
the heart with a sort of necessary inhumanity, 
the use of cutting-instruments upon our fel- 
low-creatures. 

Besides the knowledge of our body, through 
all the variety of its structure and operations in 
a sound state, it is by anatomy only that we 
can arrive at the knowledge of the true nature 
of most of the diseases which afflict humanity. 
The symptoms of many disorders are often 
equivocal ; and diseases themselves are thence 
frequently mistaken, even by sensible, expe- 
rienced, and attentive physicians. But by ana- 
tomical examination after death, we can with 
certainty find out the mistake, and learn to 
avoid it in any similar case. 

This use of anatomy has been so generally 
adopted by the moderns, that the cases alrea- 
dy published are almost innumerable : Man- 
getus, Morgagni, indeed many of the best mo- 
dern writings in physic, are full of them. And 
if we look among the physicians of the best 
character, and observe those who have the 
art itself, rather than the craft of the profes- 
sion at heart ; we shall find them constantly 
taking pains to procure leave to examine the 
bodies of their patients after death. 

After having considered the rise and pro- 
gress of anatomy; the various discoveries 
that have been made in it, from time to time ; 
the great number of diligent observers who 
have applied themselves to this art ; and the 



Introduction to Anatomy. 45 

importance of the study, not only for the pre- 
vention and cure of diseases, but in furnish- 
ing the liveliest proofs of divine wisdom; the 
following questions seem naturally to arise: 
For what purpose is there such a variety of 
parts in the human body ? Why such a com- 
plication of nice and tender machinery ? Why 
was there not rather a more simple, less deli- 
cate, and less expensive frame ?* 

In order to acquire a satisfactory general 
idea of this subject, and find a solution of all 
such questions, let us, in our imaginations, 
make a man : in other words let us suppose 
that the mind, or immaterial part, is to be 
placed in a corporeal fabric, in order to hold 
a correspondence with other material beings 
by the intervention of the body; and then 
consider, a priori, what will be wanted for her 
accommodation. In this inquiry, we shall 
plainly see the necessity or advantage, and 
therefore the final cause, of most of the parts 
which we actually find in the human body. 
And if we consider that, in order to answer 
some of the requisites, human wit and inven- 
tion would be very insufficient ; we need not 
be surprised if we meet with some parts of 
the body whose use we cannot yet perceive, and 
with some operations and functions which we 
cannot explain. We can see that the whole 
bears the most striking characters of excelling 
wisdom and ingenuity : but the imperfect sen- 

* The following beautiful representation is taken from the late 
Dr. Hunter's Introductory Lecture in Anatomy. 



46 Introduction to Anatomy. 

ses and capacity of man cannot pretend to 
reach every part of a machine, which nothing 
less than the intelligence and power of the 
Supreme Being could contrive and execute. 

First, then, the mind, the thinking, imma- 
terial agent, must be provided with a place of 
immediate residence, which shall have all the 
requisites for the union of spirit and body ; 
accordingly she is provided with the brain, 
where she dwells as governor and superintend- 
ant of the whole fabric. 

In the next place, as she is to hold a corre- 
spondence with all the material beings around 
her, she must be supplied with organs fitted 
to receive the different kinds of impressions 
which they will make. In fact, therefore, we 
see that she is provided with the organs of 
sense, as we call them : the eye is adapted to 
light ; the ear to sound ; the nose to smell ; 
the mouth to taste ; and the skin to touch. 

Further : She must be furnished with or- 
gans of communication between herself in the 
brain and those organs of sense, to give her 
information of all the impressions that are 
made upon them: and she must have organs 
between herself in the brain and every other 
part of the body, fitted to convey her com- 
mands and influence over the whole. For 
these purposes the nerves are actually given. 
They are chords, which rise from the brain, 
the immediate residence of the mind, and dis- 
perse themselves in branches through all parts 
of the body. They convey all the different 
kinds of sensations to the mind, in the brain ; 



Introduction to Anatomy. 47 

and likewise carry out from thence all her com- 
mands or influence to the other parts of the 
body. They are intended to be occasional mo- 
nitors against all such impressions as might en- 
danger the well-being of the whole, or of any 
particular part ; which vindicates the Creator 
of all things, in having actually subjected us 
to those many disagreeable and painful sensa- 
tions which we are exposed to from a thousand 
accidents in life. 

Moreover, the mind, in this corporeal sys- 
tem, must be endued with the power of mov- 
ing from place to place, that she may have in- 
tercourse with a variety of objects ; that she 
may fly from such as are disagreeable, danger- 
ous or hurtful, and pursue such as are plea- 
sant or useful to her. And accordingly she is 
furnished with limbs, and with muscles and 
tendons, the instruments of motion, which are 
found in every part of the fabric where motion 
is necessary. 

But to support, to give firmness and shape 
to the fabric ; to keep the softer parts in their 
proper places ; to give fixed points for, and the 
proper direction to its motions, as well as to 
protect some of the more important and tender 
organs from external injuries ; there must be 
some firm prop-work interwoven through the 
whole. And, in fact, for such purposes the 
bones are given. 

The prop-work must not be made into one 
rigid fabric, for that would prevent motion. 
Therefore there are a number of bones. 



48 Introduction to Anatomy. 

These pieces must all be firmly bound toge- 
ther, to prevent their dislocation. And this 
end is perfectly well answered by the liga- 
ments. 

The extremities of these bony pieces, where 
they move and rub upon one another, must 
have smooth and slippery surfaces for easy 
motion. This is most happily provided for, 
by the cartilages and mucus of the joints. 

The interstices of all those parts must be 
filled up with some soft and ductile matter, 
which shall keep them in their places, unite 
them, and at the same time allow them to move 
a little upon one another. And these purposes 
are answered by the cellular membrane or adi- 
pose substance. 

There must be an outward covering over 
the whole apparatus, both to give it compact- 
ness and to defend it from a thousand injuries : 
which, in fact, are the very purposes of the 
skin and other integuments. 

Lastly, the mind being formed for society 
and intercourse with beings of her own kind, 
she must be endued with powers of expressing 
and communicating her thoughts by some sen- 
sible marks or signs ; which shall be both easy 
to herself, and admit of great variety ; and ac- 
cordingly she is provided with the organs and 
faculty of speech, by which she can throw out 
signs with amazing facility, and vary them with- 
out end. 

Thus we have built up an animal body which 
would seem to be pretty complete : but as it 
is the nature of matter to be altered and work- 



Introduction to Anatomy. 49 

ed upon by matter ; so in a very little time such 
a living creature must be destroyed, if there is 
no provision for repairing the injuries which 
she must commit upon herself, and those which 
she must be exposed to from without. There- 
fore a treasure of blood is actually provided in 
the heart and vascular system, full of nutritious 
and healing particles, fluid enough to penetrate 
into the minutest parts of the animal ; impelled 
by the heart, and conveyed by the arteries, it 
washes every part, builds up what was broken 
down, and sweeps away the old and useless 
materials. Hence we see the necessity or ad- 
vantage of the heart and arterial system. 

What more there was of this blood than 
enough to repair the present damages of the 
machine, must not be lost, but should be re- 
turned again to the heart ; and for this purpose 
the venous system is actually provided. These 
requisites in the animal explain, a priori, the 
circulation of the blood. 

The old materials which were become use- 
less, and are swept off by the current of blood, 
must be separated and thrown out of the sys- 
tem. Therefore glands, the organs of Secre- 
tion, are given for straining whatever is redun- 
dant, vapid, or noxious, from the mass of 
blood ; and when strained, they are thrown 
out by emunctories, called organs of Excre- 
tion. 

But now, as the machine must be constant- 
ly wearing, the reparation must be carried on 
without intermission, and the strainers must 
always be employed. Therefore there is ac- 

G 



50 Introduction to Anatomy. 

tually a perpetual circulation of the blood, and 
the secretions are always going on. 

Even all this provision, however, would not 
be sufficient ; for that store of blood would 
soon be consumed, and the fabric would break 
down, if there were not a provision made for 
fresh supplies. These we observe, in fact, are 
profusely scattered round her in the animal 
and vegetable kingdoms ; and she is furnished 
with hands, the fittest instruments that could 
have been contrived, for gathering them, and 
for preparing them in a variety of ways for the 
mouth. 

But these supplies, which we call food, 
must be considerably changed ; they must be 
converted into blood. Therefore she is pro- 
vided with teeth for cutting and bruising the 
food, and with a stomach for melting it down : 
In short, with all the organs subservient to di- 
gestion. — The finer parts of the aliments only 
can be useful in the constitution : these must 
be taken up and conveyed into the blood, and 
the dregs must be thrown off. With this view 
the intestinal canal is actually given. It sepa- 
rates the nutritious part, which we call chyle, 
to be conveyed into the blood by the system 
of absorbent vessels ; and the fieces pass down- 
wards, to be conducted out of the body. 

Now we have got our animal not only fur- 
nished with what is wanted for its immediate 
existence, but also with the powers of protract- 
ing that existence to an indefinite length of 
time. But its duration, we may presume, must 
necessarily be limited: for as it is nourished, 



Introduction to Anatomy. 51 

grows, and is raised up to its full strength and 
utmost perfection ; so it must, in time, in com- 
mon with all material beings, begin to decay, 
and then hurry on to final ruin. Hence we 
see the necessity of a scheme for renovation. 
Accordingly wise Providence, to perpetuate, 
as well as preserve his work, besides giving a 
strong appetite for life and self-preservation, 
has made animals male and female, and given 
them such organs and passions as will secure 
the propagation of the species to the end of 
time. 

Thus we see, that by the very imperfect 
survey which human reason is able to take of 
this subject, the animal man must necessarily 
be complex in his corporeal system, and in its 
operations. 

He must have one great and general system, 
the vascular, branching through the whole for 
circulation : Another the nervous, with its ap- 
pendages the organs of sense, for every kind 
of feeling: And a third, for the union and 
connection of all those parts. 

Besides these primary and general systems, 
he requires others which may be more local, 
or confined : One for strength, support, and 
protection ; the bony compages : Another for 
the requisite motions of the parts among them- 
selves, as well as for moving from place to 
place ; the muscular part of the body : Ano- 
ther to prepare nourishment for the daily re- 
cruit of the body ; the digestive organs : And 
one for propagating the species ; the organs of 
generation. 



52 Introduction to Anatomy. 

And in taking this general survey of what 
would appear, a priori, to be necessary for 
adapting an animal to the situations of life, we 
observe with great satisfaction, that man is 
accordingly made of such systems, and for 
such purposes. He has them all ; and he has 
nothing more, except the organs of respira- 
tion. Breatning it seemed difficult to account 
for a priori : we only knew it to be in fact 
essentially necessary to life. Notwithstanding 
this, when we saw all the other parts of the bo- 
dy, and their functions, so well accounted for, 
and so wisely adapted to their several purpo- 
ses, there could be no doubt that respiration 
was so likewise : And accordingly, the disco- 
veries of Dr. Priestley have lately thrown 
light upon this function also, as will be shown 
in its proper place. 

Of all the different systems in the human 
body, the use and necessity are not more ap- 
parent, than the wisdom and contrivance which 
has been exerted in putting them all into the 
most compact and convenient form : in dispos- 
ing them so, that they shall mutually receive, 
and give helps to one another ; and that all, or 
many of the parts, shall not only answer their 
principal end or purpose, but operate success- 
fully and usefully in a variety of secondary 
ways. 

If we consider the whole animal machine 
in this light, and compare it with any machine 
in which human art has exerted its utmost; 
suppose the best constructed ship that ever 
was built, we shall be convinced beyond the 



Introduction to Anatomy. 53 

possibility of doubt, that there are intelligence 
and power far surpassing what humanity can 
boast of. 

One superiority in the natural machine is 
peculiarly striking. — In machines of human 
contrivance or art, there is no internal power, 
no principle in the machine itself, by which it 
can alter and accommodate itself to any injury 
which it may suffer, or make up any injury 
which admits of repair. But in the natural 
machine, the animal body, this is most won- 
derfully provided for, by internal powers in 
the machine itself; many of which are not 
more certain and obvious in their effects, than 
they are above all human comprehension as to 
the manner and means of their operation. 
Thus, a wound heals up of itself; a broken 
bone is made firm again by a callus ; a dead 
part is separated and thrown off; noxious juic- 
es are driven out by some of the emunctories ; 
a redundancy is removed by some spontane- 
ous bleeding ; a bleeding naturally stops of it- 
self; and a great loss of blood, from any cause, 
is in some measure compensated, by a con- 
tracting power in the vascular system, which 
accommodates the capacity of the vessels to 
the quantity contained. The stomach gives 
information when the supplies have been ex- 
pended ; represents, with great exactness, the 
quantity and the quality of what is wanted in 
the present state of the machine ; and in pro- 
portion as she meets with neglect, rises in her 
demand, urges her petition in a louder tone, 
and with more forcible arguments. For its 



54 Introduction to Anatomy.. 

protection, an animal body resists heat and 
cold in a very wonderful manner, and pre- 
serves an equal temperature in a burning and 
in a freezing atmosphere. 

A farther excellence or superiority in the 
natural machine, if possible, still more aston- 
ishing, more beyond all human comprehen- 
sion, than what we have been speaking of, is 
the following. Besides those internal powers 
of self-preservation in each individual, when 
two of them co-operate, or act in concert, they 
are endued with powers of making other ani- 
mals or machines like themselves, which again 
are possessed of the same powers of produc- 
ing others, and so of multiplying the species 
without end. 

These are powers which mock all human in- 
vention or imitation. They are characteris- 
tics of the divine Architect. 

Having premised this general account of the 
subject, we shall next consider the method to 
be observed in treating it. 

The study of the human body, as already 
noticed, is commonly divided into two parts. 
The first, which is called Anatomy, relates to 
the matter and structure of its parts ; the se- 
cond, called Physiology and Animal (economy, 
relates to the principles and laws of its inter- 
nal operations and functions. 

As the body is a compound of solids and 
fluids, Anatomy is divided into, 

1. The Anatomy of the solids, and 

2. The Anatomy of the fluids. 



Introduction to Anatomy. 55 

I. The Solids, by which we mean all parts 
of our body, which are not fluid, are general- 
ly divided into two classes, viz. 

1. The hard solids or bones. This part of 
anatomy is called Osteology; which signifies 
the doctrine of the bones. 

2. The softer solids; which part is called 
Sarcology, viz. the doctrine of flesh. 

This division of the solids, we may observe, 
has probably taken its origin from the vulgar 
observation, that the body is made of bone 
and flesh. And as there are many different 
kinds of what are called soft or fleshy parts, 
Sarcology is subdivided into, 

(l.) Angeiology , or the doctrine of vessels; 
by which is commonly understood blood-vessels : 

(2.) Adenology, of glands : 

(3.) Neurology, of nerves : 

(4.) Myology, of muscles : and, 

(5.) Splanchnology, of the viscera or bow- 
els. There is, besides, that part which treats 
of the organs of sense and of the integuments. 

This division of the solids has been here 
mentioned, rather for the sake of explaining 
so many words, which are constantly used 
by anatomists, than for its importance or ac- 
curacy. For besides many other objections 
that might be urged, there are in the body 
three species of solids, viz. gristle or carti- 
lage, hair, and nails ; which are of an inter- 
mediate nature between bone and flesh ; and 
therefore cannot so properly be brought into 
the osteology or the sarcology. The cartila- 
ges were classed with the bones ; because the 



56 Introduction to Anatomy. 

greatest number of them are appendages to 
bones : and for the like reason the hair and the 
nails were classed with the integuments. 

II. The Fluids of the human body may be 
divided into three kinds, which Dr. Hunter 
calls the crude, the general or perfect, and the 
local or secreted fluid. 

1. By the crude fluid is meant the chyle, and 
whatever is absorbed at the surfaces of the 
body ; in other words, what is recently taken 
into the body, and is not yet mixed with or 
converted into blood. 

2. The general or perfect fluid is the blood 
itself; to wit, what is contained in the heart, 
arteries, and veins, and is going on in the 
round of the circulation. 

3. The local or secreted, are those fluids pe- 
culiar to particular parts of the body, which 
are strained off from the blood, and yet are 
very different in their properties from the blood. 
They are commonly called secretions; and 
some are useful, others excrementitious. 

In treating of the Physiology, it is very dif- 
ficult to say what plan should be followed ; 
for every method which has been yet proposed, 
is attended with manifest inconvenience. The 
powers and operations of the machine have 
such a dependence upon one another, such 
connections and reciprocal influence, that they 
cannot well be understood or explained sepa- 
rately. In this sense our body may be com- 
pared to a circular chain of powers, in which 
nothing is first or last, nothing solitary or in- 
dependent ; so that wherever we begin, we 



Osteology. 57 

find that there is something preceding which 
we ought to have known. If we begin with 
the brain and the nerves, for example, we 
shall find that these cannot exist, even in idea, 
without the heart: if we set out with the heart 
and vascular system, we shall presently be 
sensible, that the brain and nerves must be 
supposed: or, should we take up the mouth, 
and follow the course of the aliment, we should 
see that the very first organ which presents 
itself, supposed the existence of both the heart 
and brain : Wherefore we shall incorporate the 
Physiology with the Anatomy, by attempting 
to explain the functions after we have demon- 
strated the organs. 



Part I. OSTEOLOGY. 



WE begin with the bones, which may be 
considered as the great support of the 
body, tending to give it shape and firmness. — 
But before we enter into the detail of each par- 
ticular bone, it will be necessary to describe 
their composition and connections, and to ex- 
plain the nature of the different parts which 
have an immediate relation to them ; as the car- 
tilages, ligaments, periosteum, marrow, and 
synovial glands. 

H 



58 Osteology. 



Sect. I. Of the Bones in general, with their 
Appendages, &c. 

The bones are of a firm and hard* sub- 
stance, of a white colour, and perfectly insen- 
sible. They are the most compact and solid 
parts of the body, and serve for the attachment 
and support of all the other parts. 

Three different substances are usually dis- 
tinguished in them ; their exterior or bony 
part, properly so called ; their spongy cells ; 
and their reticular substance. The first of these 
is formed of many laminae or plates, compos- 
ing a firm hard substance — The spongy or 
cellular part is so called on account of its re- 
semblance to a sponge, from the little cells 
which compose it. This substance forms al- 
most the whole of the extremities of cylindrical 
bones. The reticular part is composed of fi- 
bres, which cross each other in different direc- 
tions. This net-work forms the internal sur- 
face of those bones which have cavities. 

The flat bones, as those of the head, are 
composed only of the laminse and the cellular 
substance. This last is usually found in the 
middle of the bone dividing it into two plates, 
and is there called diploe. 



* Mr. Scheele has lately difcovered that bones contain the 
phofphoric acid united with calcareous earth ; and that to this 
combination they owe their firmnefs. 



Osteology. 59 

Gagliardi, who pretended to have discover- 
ed an infinite number of claviculi* or bony 
processes, which he describes as traversing 
the laminae to unite them together, has endea- 
voured to support this pretended discovery by 
the analogy of bones to the bark of trees, in 
which certain woody nails have been remark- 
ed ; but this opinion seems to be altogether 
fanciful. 

Some writers have supposed, that the 
bones are formed by layers of the perioste- 
um, which gradually ossify, in the same man- 
ner as the timber is formed in trees by the 
hardening of the white substance that is found 
between the inner bark and the wood. M. 
Duhamel, who has adopted this opinion, fed 
different animals with madder and their ordi- 
nary food alternately during a certain time ; 
and he asserts, that in dissecting their bones, 
he constantly observed distinct layers of red 
and white, which corresponded with the length 
of time they had lived on madder or their 
usual aliment. But it has since been proved 
by Detleff, that M. Duhamel's experiments 
were inaccurate, and that neither the perios- 
teum nor the cartilages are tinged by the use 
of madder, which is known to affect the bones 
only. 

We usually consider in a bone, its body 
and its extremities. The ancients gave the 

* Tn his Anat. Oflium nov. invent, illuftrat. he defcribes four 
kinds of theic claviculi or nails, viz. the perpendicular, oblique, 
headed, and crooked. 



60 Osteology. 

name of diaphysis to the body or middle part, 
and divided the extremities into apophysis and 
epiphysis. An apophysis, or process, as it 
is more commonly called, is an eminence con- 
tinued from the body of the bone, whereas an 
epiphysis is at first a sort of appendage to the 
bone, by means of an intermediate cartilage. 
Many epiphyses, which appear as distinct 
bones in the foetus, afterwards become apophy- 
ses ; for they are at length so completely unit- 
ed to the body of the bone as not to be distin- 
guishable from it in the adult state. It is not 
unusual, however, at the age of 1 8 and even 
20 years, to find the extremities of bones still 
in the state of epiphysis. 

The names given to the processes of bones 
are expressive of their shape, size, or use ; 
thus if a process is large and of a spherical 
form, it is called caput, or head ; if the head 
is flatted, it is termed condyle. Some proces- 
ses, from their resemblance to a stiletto, a 
breast, or the beak of a crow, are called styloid, 
mastoid, or coracoid : others are styled ridges 
or spines. The two processes of the os femo- 
ris derive their name of trochanters from their 
use. 

A bone has its cavities as well as processes. 
These cavities either extend quite through its 
substance, or appear only as depressions. The 
former are called foramina or holes, and theso 
foramina are sometimes termed canals or con- 
duits, according to their form and extent. Of 
the depressions, some are useful in articula- 
tion. These are called cotyloid when they are 



Osteology. 61 

deep, as is the case with the os innominatum, 
where it receives the head of the os femoris; 
or glenoid when they are superficial, as in ihe 
scapula, where it receives the os humeri. Of 
the depressions that are not designed for arti- 
culation, those which have small apertures are 
called sinuses; others that are large, and not 
equally surrounded by high brims, are styled 
fossa ; such as are long and narrow, furrows ; 
or if broad and superficial without brims, si- 
nuosities. Some are called digital impressions , 
from their resemblance to the traces of a fin- 
ger on soft bodies. 

We shall abridge this article, which is ex- 
ceedingly diffuse in the generality of anatomi- 
cal books, and will endeavour to describe it 
with all the clearness it will allow. 

The bones composing the skeleton are so 
constructed, that the end of every bone is per- 
fectly adapted to the extremity of that with 
which it is connected, and this connection 
forms what is called their articulation. 

Articulation is divided into diarthrosis, sy- 
narthrosis, and amphiarthrosis, or moveable, 
immovable, and mixed articulation. Each of 
the two first has its subdivisions. Thus the 
Diarthrosis, or moveable articulation, includes, 
1. The enarthrosis, as it is called, when a 
large head is admitted into a deep cavity, as 
in the articulation of the os femoris with the 
os innominatum. 2. Arthrodia, when a round 
head is articulated with a superficial cavity, as 
is the case of the os humeri and scapula. 3. 
Ginglimus, or hinge-like articulation, as in the 



62 Osteology. 

connection of the thigh-bone with the tibia. 
The enarthrosis and arthrodia allow of motion 
to all sides ; the ginglimus only of flection and 
extension. 

The synarthrosis, or immoveable articula- 
tion, includes, 1. The suture, when the two 
bones are indented into each other, as is the 
case with the parietal bones. 2. Gomphosis, 
when one bone is fixed into another, in the 
manner the teeth are placed in their sockets. 

The term amphiarthrosis is applied to those 
articulations which partake both of the synar- 
throsis and diarthrosis, as is the case with thu 
bones of the vertebrae, which are capable of 
motion in a certain degree, although they are 
firmly connected together by intermediate car- 
tilages. 

What is called symphysis is the union of 
two bones into one ; as in the lower jaw, for 
instance, which in the foetus consists of two 
distinct bones, but becomes one in a more ad- 
vanced age, by the ossification of the uniting 
cartilage. 

When bones are thus joined by the means 
of cartilages, the union is styled synchondro- 
sis ; when by ligaments, syneurosis. 

Cartilages are white, solid, smooth, and 
elastic substances, between the hardness of 
bones and ligaments, and seemingly of a fi- 
brous texture. We are not able to trace any 
vessels into their substance by injection, nor 
are they ever found tinged in animals that have 
been fed with madder. 



Osteology. 63 

They may be distinguished into, 1st, Those 
which are connected with the bones ; and, 
2dly, Those" which belong to other parts of 
the body. The first serve either to cover the 
ends and cavities of bones intended for mo- 
tion, as in the articulations, where by their 
smoothness they facilitate motions, which the 
bones alone could not execute with so much 
freedom ; or they serve to unite bones toge- 
ther, as in the symphysis pubis, or to length- 
en them, as in the ribs. 

Many of them ossifying as we advance in 
life, their number is less in the adult than in 
the foetus, and of course there are fewer bones 
in the old than in the young subject. 

Of the second class of cartilages, or those 
belonging to the soft parts, we have instances 
in the larynx, where we find them useful in 
the formation of the voice, and for the attach- 
ment of muscles. 

The periosteum is a fine membrane of a 
compact cellular texture, reflected from one 
joint to another, and serving as a common 
covering to the bones. It has sanguiferous 
and lymphatic vessels, and is supplied with 
nerves from the neighbouring parts. It ad- 
heres very firmly to their surface, and by its 
smoothness facilitates the motion of muscles. 
It likewise supports the vessels that go to be 
distributed through the substance of the bones, 
and may serve to strengthen the articulations. 
At the extremities of bones, where it is found 
covering a cartilage, it has by some been im- 
properly considered as a distinct membrane, 



64 Osteology. 

and named perichondrium. This, in its use 
and structure, resembles the periosteum. 
Where it covers the bones of the skull, it 
has gotten the name of pericranium. 

The periosteum is not a production of the 
dura mater, as the ancients, and after them 
Havers, imagined; nor are the bones formed 
by the ossification of this membrane, at least 
when it is in a sound state, as some late wri- 
ters have supposed. 

The periosteum is deficient in the teeth 
above the sockets, and in those parts of bones 
to which ligaments or tendons are attached. 

The marrow is a fat oily substance, filling 
the cavities of bones. In the great cavities of 
long bones it is of a much firmer consistence 
than in the cells of their spongy part. In the 
former it inclines somewhat to a yellowish 
tinge, and is of the consistence of fat ; in the 
latter it is more fluid, and of a red colour. 
This difference in colour and consistence is 
owing to accidental causes ; both kinds are of 
the same nature, and may both be described 
under the common name of marrow, though 
some writers give the name only to the fat-like 
substance, and call the other the medullary 
juice. 

The marrow is contained in a very fine and 
transparent membrane, which is supplied with 
a great number of blood-vessels, chiefly from 
the periosteum. This membrana medullaris 
adheres to the inner surface of the bones, 
and furnishes an infinite number of minute 
bags or vesicles for inclosing the marrow, 



Osteology. 6 5 

which is likewise supported in the cavities of 
the bones by the long filaments of their reti- 
cular substance. 

Besides the vessels from the periosteum, 
the membrana medullaris is furnished with 
others, which in the long bones may be seen 
passing in near the extremities of the bone, 
and sending off numerous branches that rami- 
fy through all the vesicles of this membrane. 

The bones, and the cells containing the 
marrow, are likewise furnished with lympha- 
tics. By their means, the marrow, like the 
fat, may be taken up in a greater quantity than 
it is secreted ; and hence it is that so little is 
found in the bones of those who die of linger- 
ing diseases. 

It is still a matter of controversy, Whether 
the marrow is sensible or not? We are cer- 
tainly not able to trace any nerves to it; and 
from this circumstance, and its analogy to fat, 
Haller has ventured to consider it as insensi- 
ble. On the other hand, Duverney asserts, 
that an injury done to this substance in a liv- 
ing animal was attended with great pain. In 
this dispute physiologists do not seem to have 
sufficiently discriminated between the marrow 
itself and the membranous cells in which it is 
contained. The former, like the fat, being 
nothing more than a secreted, and of course 
an inorganized, matter, may with propriety be 
ranked among the insensible parts, as much as 
inspissated mucus or any other secreted mat- 
ter in the body ; whereas the membrana me- 
dullaris being vascular, though it possesses but 

I 



(36 Osteology. 

an obscure degree of feeling in a sound state, 
is not perfectly insensible. 

The marrow was formerly supposed to be 
intended for the nourishment and renewal of 
the bones ; but this doctrine is now pretty ge- 
nerally and deservedly exploded. It seems 
probable that the marrow is to the bones what 
fat is to the soft parts. They both serve for 
some important purposes in the animal cecono- 
my ; but their particular use has never yet 
been clearly ascertained. The marrow, from 
the transudation of the oil through the bones 
of a skeleton, is supposed to diminish their 
brittleness ; and Havers, who has written pro- 
fessedly on the bones, describes the canals by 
which the marrow is conveyed through every 
part of their substance, and divides them into 
longitudinal and transverse ones. He speaks 
of the first as extending through the whole 
length of the bone; and of the latter, as the 
passages by which the longitudinal ones com- 
municate with each other. The similarity of 
these to the large cancelli in burnt bones, and 
the transudation of the oil through the bones 
of the skeleton, seems to prove that some such 
passages do actually exist. 

The synovial glands are small bodies,* sup- 
posed to be of a glandular structure, and ex- 
ceedingly vascular, secreting a fluid of a clear 
mucilaginous nature, which serves to lubricate 
the joints. They are placed in small cavities 

* Tt is now much doubted, however, whether the appear- 
ances in the joints, which arc usually called glands % are any thing 
more than assemblages of fat. 



Osteology. 67 

in the articulations, so as to be capable of be- 
ing gently compressed by the motion of the 
joint, which expresses their juice in propor- 
tion to the degree of friction. When the sy- 
novia is wanting, or is of too thick a consist- 
ence, the joint becomes stiff and incapable of 
flexion or extension. This is what is termed 
anchilosis. 

Ligaments are white, glistening, inelastic 
bands, of a compact substance, more or less 
broad or thick, and serving to connect the 
bones together. They are distinguished by 
different names adapted to their different forms 
and uses. Those of the joints are called ei- 
ther round or bursal. The round ligaments 
are white, tendinous, and inelastic. They are 
strong and flexible, and are found only in the 
joint of the knee, and in the articulation of the 
os femoris with the os innominatum. The 
bursal, or capsular ligaments, surround the 
whole joint like a purse, and are to be found 
in the articulations which allow motion every 
way, as in the articulation of the arm with the 
scapula. 

Of those sacs called Bursa mucosa?, a. few 
were known to former anatomists, but by much 
the greater number have been since discover- 
ed by Dr. Monro,* who observes, that they 
are to be met with in the extremities of the 
body only; that many of them are placed en- 
tirely on the inner sides of the tendons, be- 
tween these and the bones. Many others co- 
ver not only the inner, but the outer sides of 

* See DescripicTi of the Bttrsx Mucosa, See. 



68 Osteology. 

the tendons, or are interposed between the ten- 
dons and external parts, as well as between 
those and the bones. 

Some are situated between the tendons and 
external parts only or chiefly, some between 
contiguous tendons, or between the tendons 
or the ligaments and the joints. A few such 
sacs are observed where the processes of bones 
play upon the ligaments, or where one bone 
plays upon another. Where two or more ten- 
dons are contiguous, and afterwards separate 
from each other, we generally find a common 
bursa divided into branches, with which it 
communicates ; and a few bursse of contigu- 
ous tendons communicate with each other. — 
Some in healthy children, communicate with 
the cavities of the joints ; and in many old 
people he has seen such communications form- 
ed by use or worn by friction, independent of 
disease. 

Their proper membrane is thin and trans- 
parent, but very dense, and capable of con- 
fining air or any other fluid. It is joined to the 
neighbouring parts by the common cellular sub- 
stance. Between the bursa and the hard sub- 
stance of bone, a thin layer of cartilage or 
of tough membrane is very generally interpos- 
ed. To the cellular substance on the outside 
of the bursa, the adipose substance is con- 
nected; except where the bursa covers a ten- 
don, cartilage, or bone, much exposed to pres- 
sure or friction. 

In several places a mass of fat, covered 
with the continuation of the membrane of the 



Osteology. 69 

bursa, projects into its cavity. The edges 
of this are divided into fringes. 

The inner side of the membrane is smooth, 
and is extremely slippery from the liquor se- 
creted in it. 

The structure of the buf sae bears a strong 
resemblance to the capsular ligaments of the 
joints. 1. The inner layer of the ligament, 
like that of the bursas, is thin and dense. 2. 
It is connected to the external ligaments by 
the common cellular substance. 3. Between 
it and the bones, layers of cartilage, or the 
articular cartilages, are interposed. 4. At the 
sides of the joints, where it is not subjected 
to violent pressure and friction, the adipose 
substance is connected with the cellular mem- 
brane. 5. Within the cavities of the joints 
we observe masses of fat projecting, covered 
with similar blood-vessels, and with similar 
fimbria? hanging from their edges. 6. In the 
knee the upper part of such a mass of fat 
forms what has been called the mucilaginous 
gland of the joint, and the under part projects 
into the bursa behind the ligament which ties 
the patella to the tibia. 7. The liquor which 
lubricates the bursas has the same colour, con- 
sistence, and properties as that of the joints, 
and both are affected in the same manner by 
heat, mineral acids, and ardent spirits. 8. In 
some places the bursa? constantly communi- 
cate with the cavities of the joints, in others 
they generally do so ; from which we may in- 
fer a sameness of structure. 

When we examine the fimbria? common to 
the fatty bodies of the joints and bursa?, and 



70 Osteology. 

which have been supposed to be the ducts of 
glands lodged within the masses of fat, we 
are not able to discover any glandular appear- 
ance within them. And although we observe 
many vessels dispersed upon the membranes 
of the fatty bodies and fimbrise ; and that we 
cannot doubt that these fimbrise consist of ducts 
which contain a lubricating liquor, and can 
even press such a liquor from them ; yet their 
cavities and orifices are so minute, that they 
are not discoverable even by the assistance 
of magnifying-glasses. These fimbrise appear, 
therefore, to be ducts like those of the ure- 
thra, which prepare a mucilaginous liquor, 
without the assistance of any knotty or glan- 
dular organ. 

Upon the whole, the synovia seems to be 
furnished by invisible exhalent arteries by the 
ducts of the fimbriae, and by oil exuding from 
the adipose follicles by passages not yet disco- 
vered. 

The word skeleton, which by its etymology 
implies simply a dry preparation, is usually 
applied to an assemblage of all the bones of 
an animal united together in their natural or- 
der. It is said to be a natural skeleton, when 
the bones are connected together by their own 
proper ligaments ; and an artificial one, when 
they are joined by any other substance, as 
wire, &c. 

The skeleton is generally divided into the 
head, trunk, and extremities. The first divi- 
sion includes the bones of the cranium and 
face. The bones of the trunk are the spine, 
ribs, sternum, and bones of the pelvis. 



Osteology. 71 

The upper extremity on each side consists 
of the two bones of the shoulder, viz. the sca- 
pula and clavicle ; the bone of the arm, or os 
humeri; the bones of the fore-arm, and those 
of the hand. 

The lower extremity on each side of the 
trunk consists of the thigh-bone and the bones 
of the leg and foot. 



Sect. II. Of the Bones of the Head. 

The head is of a roundish figure, and some- 
what oval.* Its greatest diameter is from the 
forehead to the occiput ; its upper part is call- 
ed vertex, or crown of the head ; its anterior 
or fore-part the face ; and the upper part of 
this sinciput, or forehead ; its sides the tem- 
ples ; its posterior, or hind-part, the occiput ; 
and its inferior part the basis. 

The bones of the head may be divided into 
those of the cranium and face. 

* The hones of the fcetus being perfectly distinct, and the 
muscles in young persons not acting much, the shape of the 
head has been supposed to depend much on the management of 
children when very young. Vesalius, who has remarked the dif- 
ference in people of different nations, observes, for instance, that 
the head of a Turk is conical, from the early use of the turban; 
whilst that of an Englishman is flattened by the chin-stay. Some 
of the latest physiologists suppose, with good reason, that this 
difference is chiefly owing to certain natural causes with which 
wc are as yet unacquainted. 



7 2 Osteology. 



1. Bones of the Cranium and Face, 

There are eight bones of the cranium, viz. 
the coronal bone, or os frontis ; the two pari- 
etal bones, or ossa bregmatis ; the os occipi- 
tis ; the two temporal bones ; the sphenoid 
bone ; and the os ethmoides, or cribriforme. 

Of these, only the os occipitis and ossa 
bregmatis are considered as proper to the cra- 
nium ; the rest being common both to the cra- 
nium and face. 

These bones are all harder at their surface 
than in their middle ; and on this account they 
are divided into two tables, and a middle spon- 
gy substance called diplbe. 

In this, as in all the other bones, we shall 
consider its figure, structure, processes, de- 
pressions, and cavities ; and the manner in 
which it is articulated with the other bones. 

The os frontis has some resemblance in 
shape to the shell of the cockle. Externally it 
is convex, its concave side being turned to- 
wards the brain. This bone, in the places 
where it is united to the temporal bones, is 
very thin, and has there no diplbe. It is like- 
wise exceedingly thin in that part of the orbit 
of the eye which is nearest to the nose. Hence 
it is, that a wound in the eye, by a sword or 
any other pointed instrument, is sometimes 
productive of immediate death. In these cases, 
the sword passing through the weak part of 
the bone, penetrates the brain, and divides 
the nerves at their origin; or perhaps opens 



Osteology. 73 

some blood-vessel, the consequences of which 
are soon fatal. 

We observe on the exterior surface of this 
bone five apophyses or processes, which are 
easily to be distinguished. One of these is 
placed at the bottom and narrowest part of the 
bone, and is called the nasal process, from its 
supporting the upper end of the bones of the 
nose. The four others are called angular or 
orbitar processes. They assist to form the 
orbits, which are the cavities on which the 
eyes are placed. In each of these orbits there 
are two processes, one at the interior or great 
angle, and the other at the exterior or little 
angle of the orbit. They are called the angu- 
lar processes. Between these a ridge is ex- 
tended in form of an arch, and on this the eye- 
brows are placed. It is called the orbitar or 
superciliary ridge, and in some measure covers 
and defends the globe of the eye. There is a 
hole in this for the passage of the frontal ves- 
sels and nerves. This arch is interrupted 
near the nose by a small pit, in which the ten- 
don of the musculus obliquus major of the 
eye is fixed. From the under part of each su- 
perciliary ridge a thin plate runs a considera- 
ble way backwards, and has the name of orbi- 
tar ; the external and fore-part of this plate 
forms a sinuosity for lodging the lacrymal 
gland. Between the orbitar plates there is a 
large discontinuation of the bone, which is fill- 
ed up by the cribriform part of the os ethmoi- 
des. 

K 



74 Osteology. 

On examining the inner surface of this bone 
at its under and middle part, we observe an 
elevation in form of a ridge, which has been 
called the spinous process ; it ascends for some 
way, dividing the bone into two considerable 
fossae, in which the anterior lobes of the brain 
are placed. To a narrow furrow in this ridge 
is attached the extremity of the falx, as the 
membrane is called, which divides the brain 
into two hemispheres. The furrow becoming 
gradually wider, is continued to the upper and 
back part of the bone. It has the falx fixed to 
it, and part of the longitudinal sinus lodged in 
it. Besides the two fossae, there are many 
depressions, which appear like digital impres- 
sions, and owe their formation to the promi- 
nent circumvolutions of the brain. 

In the foetus, the forehead is composed of 
two distinct bones ; so that in them the sagit- 
tal suture reaches from the os occipitis to the 
nose. This bone is almost every where com- 
posed of two tables and a diploe. These two 
tables separating from each other under the 
eyes, form two cavities, one on each side of 
the face, called the frontal sinuses. These 
sinuses are lined with a soft membrane, called 
membrana pituitaria. In these sinuses a mu- 
cus is secreted, which is constantly passing 
through two small holes into the nostrils, which 
it serves to moisten. 

The os frontis is joined by suture to many 
of the bones of the head, viz. to the parietal, 
maxillary, and temporal bones ; to the os eth- 
moides ; os sphenoides ; os unguis ; and ossa 



Osteology. 75 

nasi. The suture which connects it with the 
parietal bones is called the coronal suture. 

The parietal bones are two in number ; they 
are very thin, and even transparent in some 
places, the particular figure of each of these 
bones is that of an irregular square, bordered 
with indentations through its whole circumfer- 
ence, except at its lower part. It will be ea- 
sily conceived, that these bones which com- 
pose the superior and lateral parts of the cra- 
nium, and cover the greatest part of the brain, 
form a kind of vault. On their inner surface 
we observe the marks of the vessels of the du- 
ra mater ; and at their upper edge the groove 
for the superior longitudinal sinus. 

The ossa parietalia are joined to each other 
by the sagittal suture ; to the os sphenoides 
and ossa temporum by the squamous suture ; 
to the os occipitis by the lambdoidal suture,* 
so called from its resemblance to the Greek 
letter lambda ; and to the os frontis by the co- 
ronal suture. 

in the foetus, the parietal bones are sepa- 
rated from the middle of the divided os frontis 
by a portion of the cranium then unossified. 

The occipital bone forms the posterior and 
inferior parts of the skull ; it approaches near- 
ly to the shape of a lozenge, and is indented 
throughout three parts of its circumference. 

* The lambdoidal suture is sometimes very irregular, being 
composed of many small sutures, which surround so many lit- 
tle bones called ossa triquetra, though perhaps improperly, as 
they are not always triangular. 



7G Osteology. 

There is a considerable hole in the inferior 
portion of this bone, called the foramen mag- 
num, through which the medulla oblongata 
passes into the spine. — The nervi accessorii, 
and vertebral arteries, likewise pass through 
it. Behind the condyles are two holes for the 
passage of cervical veins into the lateral si- 
nuses ; and above them are two others for the 
passage of the eighth pair and accessory nerves 
out of the head. At the sides, and a little on 
the anterior part of the foramen magnum, are 
two processes, called the condyles, one on 
each side ; they are of an oval figure, and are 
covered with cartilage. 

The external surface of this bone has a 
large transverse arched ridge, under which the 
bone is very irregular, where it affords attach- 
ment to several muscles. On examining its 
inner surface, we may observe two ridges in 
form of a cross ; one ascending from near the 
foramen magnum to the top of the bone ; the 
upper end of this in which the falx is fixed, is 
hollow, for lodging the superior longitudinal 
sinus, and the under end has the third process 
of the dura mater fixed to it. The other ridge, 
which runs horizontally, is likewise hollow for 
containing the lateral sinuses. Four fossae 
are formed by the cross, two above and two 
below. In the former are placed the posterior 
lobes of the brain, and in the latter the lobes 
of the cerebellum. 

At the basis of the cranium, we observe 
the cuneiform process (which is the name 
given to the great apophysis at the fore part of 



Osteology. 77 

this bone'} ; it serves for the reception of the 
medulla oblongata. 

The os occipitis is of greater strength and 
thickness, than either of the other bones of 
the head, though irregularly so ; at its inferi- 
or part, where it is thinnest, it is covered by 
a great number of muscles. 

This bone, from its situation, being more 
liable to be injured by falls, than any other 
bone of the head, nature has wisely given it 
the greatest strength at its upper part, where 
it is most exposed to danger. 

It is joined to the parietal bones by the 
lambdoidal suture, and to the ossa temporum, 
by the additamentum of the temporal suture. 
It is likewise connected to the os sphenoides 
by the cuneiform process. It is by means of 
the os occipitis that the head is united to the 
trunk, the two condyles of this bone being 
connected to the superior oblique processes 
of the first vertebra of the neck. 

There are two temporal bones, one on each 
side. — We may distinguish in them two parts; 
one of which is called the squamous or scaly 
part, and the other pars petrosa from its hard- 
ness. This last is shaped like a pyramid. 

Each of these divisions affords processes 
and cavities: externally there are three pro- 
cesses ; one anterior, called the zygomatic 
process ; one posterior, called the mastoid or 
mamillary process, from its resemblance to a 
nipple ; and one inferior, called the styloid pro- 
cess, because it is shaped like a stiletto, or dag- 
ger. 



78 Osteology. 

The cavities are, 1. The meatus auditorius 
externus. 2. A large fossa which serves for 
the articulation of the lower jaw ; it is before 
the meatus auditorius, and immediately under 
the zygomatic process. 3. The stylo-mastoid 
hole, so called from its situation between the 
styloid and mastoid processes ; it is likewise 
styled the aqueduct of Fallopius, and affords 
a passage to the portio dura of the auditory, 
or seventh pair of nerves. 4. Below, and on 
the fore-part of the last foramen, we observe 
part of the jugular fossa, in which the begin- 
ning of the internal jugular vein is lodged. An- 
terior and superior to this fossa is the orifice 
of a foramen through which passes the carotid 
artery. This foramen runs first upwards and 
then forwards, forming a kind of elbow, and ter- 
minates at the end of the os petrosum. — At this 
part of each temporal bone, we may observe, 
the opening of the Eustachian tube, a canal 
which passes from the ear to the back part of 
the nose. 

In examining the internal surface of these 
bones, we may remark the triangular figure 
of their petrous part which separates two fos- 
sae ; one superior and anterior ; the other in- 
ferior and posterior : the latter of these com- 
poses part of the fossa, in which the cerebel- 
lum is placed ; and the former, a portion of 
the least fossa for the basis of the brain. On 
the posterior side of the pars petrosa, we ob- 
serve the meatus auditorius internus, into 
which enters the double nerve of the seventh 
pair. On the under side of this process, part 
of a hole appears, which is common to the 



Osteology. 79 

temporal and occipital bones ; through it the 
lateral sinus, the eighth pair, and accessory- 
nerves, pass out of the head. 

The pars petrosa contains several little 
bones called the bones of the ear; which, as 
they do not enter into the formation of the 
cranium, shall be described when we are treat- 
ing of the organs of hearing. 

The ossa temporum are joined to the ossa 
malarum, by the zygomatic sutures ; to the pa- 
rietal bones, by the squamous sutures ; to the 
os occipitis, by the lambdoidal suture ; and to 
the sphenoid bone, by the suture of that name. 

This bone, from its situation amidst the 
other bones of the head, has sometimes been 
called cuneiforme. It is of a very irregular 
figure, and has been compared to a bat with 
its wings extended. 

It is commonly divided into its middle part 
or body, and its sides or wings. 

The fore part of the body has a spine or 
ridge, which makes part of the septum nari- 
um. The upper part of each wing forms a 
share of the temple. The fore part of this 
belongs to the orbit ; while the under and 
back part, termed spinous process, is lodged 
in the base of the skull at the point of the 
pars petrosa. But two of the most remarka- 
ble processes are the ptergoid or aliform, one 
on each side of the body of the bone, and at 
no great distance from it. Each of these pro- 
cesses is divided into two wings, and of. these 
the exterior one is the widest. The other ter- 
minates in a hook-like process. 



80 Osteology. 

The internal surface of this bone affords 
three fossae. Two of these are formed by the 
wings of the bone, and make a part of the 
lesser fossse of the basis of the cranium. The 
third, which is smaller, is on the top of the 
body of the bone ; and is called sella turcica, 
from its resemblance to a Turkish saddle. 
This fossa, in which the pituitary gland is 
placed, has posteriorly and anteriorly process- 
es called the clinoid processes. 

There are twelve holes in this bone, viz. six 
on each side. The first is the passage of the 
optic nerve and ocular artery ; the second, or 
large slit, transmits the third, fourth, sixth, 
and first part of the fifth pair of nerves with 
the ocular vein ; the third hole gives passage 
to the second branch of the fifth pair ; and the 
fourth hole to the third branch of the fifth 
pair of nerves. The fifth hole is the passage 
of the artery of the dura mater. The sixth 
hole is situated above the ptergoid process of 
the sphenoid bone; through it a reflected 
branch of the second part of the fifth pair 
passes. 

Within the substance of the os sphenoides 
there are two sinuses separated by a bony 
plate. They are lined with the pituitary mem- 
brane ; and, like the frontal sinuses, separate 
a mucus which passes into the nostrils. 

The os sphenoides is joined to all the bones 
of the cranium ; and likewise to the ossa max- 
illaria, ossa malarum, ossa palati, and vo- 
mer. 



Osteology. 81 

This bone makes part of the basis of the 
skull, assists in forming the orbits, and affords 
attachment to several muscles. 

The os ethmoides is situated at the fore 
part of the basis of the cranium, and is of a 
very irregular figure. From the great number 
of holes with which it is pierced, it is some- 
times called os cribriforme or sieve-like bone. 

It consists of a middle part and two sides. 
The middle part is formed of a thin bony- 
plate, in which are an infinite number of holes 
that afford a passage to filaments of the ol- 
factory nerve. From the middle of this plate, 
both on the outside and from within, there 
rises up a process, which may be easily 
distinguished. The inner one is called cris- 
ta galli, from its supposed resemblance to 
a cock's comb. To this process the falx of 
the dura mater is attached. The exterior pro- 
cess, which has the same common basis as the 
crista galli, is a fine lamella which is united 
to the vomer ; and divides the cavity of the 
nostrils, though unequally, it being generally 
a little inclined to one side. 

The lateral parts of this bone are compos- 
ed of a cellular substance ; and these cells are 
so very intricate, that their figure or number 
cannot be described. Many writers have on 
this account called this part of the bone the 
labyrinth. These cells are externally covered 
with a very thin bony lamella. This part of 
the bone is called the os planum, and forms 
part of the orbit. 

L 



82 Osteology, 

The different cells of this bone, which are 
numerous, and which are every where lined 
with the pituitary membrane, evidently serve 
to enlarge the cavity of the nose, in which the 
organ of smelling resides. 

This bone is joined to the os sphenoides, 
os frontis, ossa maxillaria, ossa palati, ossa 
nasi, ossa unguis, and vomer. 

The ancients, who considered the brain as 
the seat of all the humours, imagined that 
this viscus discharged its redundant moisture 
through the holes of the ethmoid bone. And 
the vulgar still think, that abscesses of the 
brain discharge themselves through the mouth 
and ears, and that snuff is liable to get into 
the head ; but neither snuff nor the matter of 
an abscess are more capable of passing 
through the cribriform bone, than the serosi- 
ty which they supposed was discharged 
through it in a common cold. — All the holes 
of the ethmoid bone are filled up with the 
branches of the olfactory nerve. Its inner 
part is likewise covered with the dura mater, 
and its cells are every where lined with the 
pituitary membrane ; so that neither matter 
nor any other fluid can possibly pass through 
this bone either externally or internally. Mat- 
ter is indeed sometimes discharged through 
the nostrils ; but the seat of the disease is in 
the sinuses of the nose, and not in the brain; 
and imposthumations are observed to take place 
in the ear, which suppurate and discharge 
themselves externally. 



Osteology. 83 

Before we leave the bones of the head, we 
wish to make some general observations on its 
structure and figure. — As the cranium might 
have been composed of a single bone, the ar- 
ticulation of its several bones being absolute- 
ly without motion, it may be asked perhaps, 
Why such a multiplicity of bones, and so 
great number of sutures? Many advantages 
may possibly arise from this plurality of bones 
and sutures, which may not yet have been 
observed. We are able, however, to point 
out many useful ends, which could only be ac- 
complished by this peculiarity of structure. — 
In this, as in all the other works of nature, the 
great wisdom of the Creator is evinced, and can- 
not fail to excite our admiration and gratitude. 

The cranium, by being divided into sever- 
al bones, grows much faster and with greater 
facility, than if it was composed of one piece 
only. In the foetus, the bones, as we have 
before observed, are perfectly distinct from 
each other. The ossification begins in the 
middle of each bone, and proceeds gradually 
to the circumference. Hence the ossification, 
and of course the increase of the head, is car- 
ried on from an infinite number of points at 
the same time, and the bones consequently ap- 
proach each other in the same proportion. To 
illustrate this doctrine more clearly, if it can 
want further illustration, suppose it necessa- 
ry for the parietal bones which compose the 
upper part of the head, to extend their ossifi- 
cation, and form the fore part of the head 
likewise. — Is it not evident, that this process 



84 Osteology. 

would be much more tedious than it is now, 
when the os frontis and the parietal bones are 
both growing at the same time ? Hence it hap- 
pens, that the Heads of young people, in which 
the bones begin to touch each other, increase 
slowly ; and that the proportionate increase of 
the volume of the head is greater in three 
months in the foetus, than it is perhaps in 
twenty -four months at the age of fourteen or 
fifteen years. 

The sutures, exclusive of their advantage 
in suspending the processes of the dura ma- 
ter, are evidently of great utility in prevent- 
ing the too great extent of fractures of the 
skull. — Suppose, for instance, that by a fall 
or blow, one of the bones of the cranium be- 
comes fractured. The fissure, which in a 
head composed of only one bone, would be 
liable to extend itself through the whole of it, 
is checked, and sometimes perhaps stopped by 
the first suture it meets, and the effects of 
the injury are confined to the bone on which 
the blow was received. Ruysch indeed, and 
some others, will not allow the sutures to be 
of any such use ; but cases have been met 
with where they seemed to have had this ef- 
fect, and in young subjects their utility in 
this respest must be still more obvious. 

The spherical shape of the head seems like- 
wise to render it more capable of resisting ex- 
ternal violence than any other shape would do. 
In a vault, the parts mutually support and 
strengthen each other, and this happens in the 
cranium. 



Osteology. 85 



1. Proper Bones of the Face. 

The face, which consists of a great number 
of bones, is commonly divided into the upper 
and lower jaws. The upper jaw consists of 
thirteen bones, exclusive of the teeth. Of 
these, six are placed on each side of the max- 
illa superior, and one in the middle. 

The bones, which are in pairs, are the os- 
sa malarum, ossa maxillaria, ossa nasi, ossa 
unguis, ossa palati, and ossa spongiosa inferi- 
ora. The single bone is the vomer. 

These are the prominent square bones which 
are placed under the eyes, forming part of 
the orbits and the upper part of the cheeks. 
Each of them affords three surfaces ; one ex- 
terior and a little convex ; a second superior 
and concave, forming the inferior part and 
sides of the orbit ; and a third posterior, irre- 
gular, and hollowed for the lodgment of the 
lower part of the temporal muscle, 

The angles of each bone form four process- 
es, two of which may be called orbitar process- 
es ; of these the upper one is joined by suture 
to the os frontis, and that below to the maxil- 
lary bone. The third is connected with the 
os sphenoides by means of the transverse su- 
ture ; and the fourth is joined to the zygoma- 
tic process of the temporal bone, with which 
it forms the zygoma. 

These bones, which are of a very irregular 
figure, are so called because they form the 
most considerable portion of the upper jaw. 



86 Osteology. 

They are two in number, and generally re- 
main distinct through life. 

Of the many processes which are to be 
seen on these bones, and which are connect- 
ed with the bones of the face and skull, we 
shall describe only the most remarkable. 

One of these processes is at the upper and 
fore part of the bone, making part of the side 
of the nose, and called the nasal process. An- 
other forms a kind of circular sweep at the in- 
ferior part of the bone, in which are the alve- 
oli or sockets for the teeth : this is called the 
alveolar process. A third process is united to 
the os mala on each side. Between this and 
the nasal process there is a thin plate, which 
forms a share of the orbit, and lies over a 
passage for the superior maxillary vessels and 
nerves. — The alveolar process has posterior- 
ly a considerable tuberosity on its internal 
surface, called the maxillary tuberosity. 

Behind the alveolar process we observe two 
horizontal lamellae, which uniting together, 
form a part of the roof of the mouth, and di- 
vide it from the nose. The hollowness of the 
roof of the mouth is owing to this partition's 
being seated somewhat higher than the alveo- 
lar process. — At the fore part of the horizon- 
tal lamellae there is a hole called foramen inci- 
sivum, through which small blood-vessels and 
nerves go between the mouth and nose. 

In viewing these bones internally, we ob- 
serve a fossa in the inferior portion of the 
^)asal process, which with the os unguis and 



Osteology. 87 

os spongiosum inferius, forms a passage for 
the lachrymal duct. 

Where these two bones are united to each 
other, they project somewhat upwards and 
forwards, leaving between them a furrow, in- 
to which the lower portion of the septum na- 
si is admitted,* 

Each of these bones being hollow, a consi- 
derable sinus is formed under its orbitar part. 
This cavity, which is usually named after 
Highmore, though it was described by Fallopi- 
us and others before his time, is lined with 
the pituitary membrane. It is intended for 
the same purposes as the other sinuses of the 
nose, and opens into the nostrils. 

The ossa maxillaria are connected with the 
greater part of the bones of the face and crani- 
um, and assist in forming not only the cheeks, 
but likewise the palate, nose, and orbits. 

The ossa nasi form two irregular squares. 
They are thicker and narrower above than 
below. Externally they are somewhat convex, 
and internally slightly concave. These bones 
constitute the upper part of the nose. At 
their fore part they are united to each other, 
above to the os frontis, by their sides to the 
ossa maxillaria superiora, posteriorly and in- 
teriorly to the septum narium, and below to 
the cartilages that compose the rest of the 
nostrils. 

These little transparent bones owe their 
name to their supposed resemblance to a fin- 
ger-nail. Sometimes they are called ossa la* 
rhrymalia, from their concurring with the na- 



88 Osteology. 

sal process of each maxillary bone in forming 
a lodgement for the lachrymal sac and duct. 

The ossa unguis are of an irregular figure. 
Their external surface consists of two smooth 
parts, divided by a middle ridge. One of these 
parts, which is concave and nearest to the 
nose, serves to support the lachrymal sac and 
part of the lachrymal duct. The other, which 
is flat, forms a small part of the orbit. 

Each of these bones is connected with the 
os frontis, os ethmoides, and os maxillare su- 
perius. 

These bones which are situated at the back 
part of the roof of the mouth, between the os 
sphenoides and the ossa maxillaria superiora, 
are of a very irregular shape, and serve to 
form the nasal and maxillary fossa, and a small 
portion of the orbit. Where they are united 
to each other, they rise up into a spine on 
their internal surface. This spine appears to 
be a continuation of that of the superior max- 
illary bones, and helps to form the septum 
narium. 

These bones are joined to the ossa maxilla- 
ria superiora, os ethmoides, os sphenoides, 
and vomer. 

This bone derives its name from its resem- 
blance to a ploughshare. It is a long and flat 
bone, somewhat thicker at its back than at its 
fore part. At its upper part we observe a 
furrow extending through its whole length. 
The posterior and largest part of this furrow- 
receives a process of the sphenoid bone. From 
this the furrow advances forwards, and be- 



Osteology. # 8 9 

coming narrower and shallower, receives some 
part of the nasal lamella ethmoidea; the rest 
serves to support the middle cartilage of the 
nose. 

The inferior portion of this bone is placed 
on the nasal spine of the maxillary and palate 
bones, which we mentioned in our description 
of the ossa palati. 

The vomer is united to the os sphenoides, 
os ethmoides, ossa maxillaria superiora, and 
ossa palati. It forms part of the septum nari- 
um, by dividing the back part of the nose into 
two nostrils. 

The parts which are usually described by 
this name, do not seem to deserve to be dis- 
tinguished as distinct bones, except in young 
subjects. They consist of a spongy lamella 
in each nostril, which is united to the spongy 
lamina of the ethmoid bone, of which they 
are by some considered as a part. 

Each of these lamellse is longest from be- 
hind forwards ; with its convex surface turn- 
ed towards the septum narium, and its con- 
cave part towards the maxillary bone, covering 
the opening of the lachrymal duct into the 
nose. 

These bones are covered with the pituitary 
membrane ; and, besides their connection with 
the ethmoid bone, are joined to the ossa max- 
illaria superiora, ossa palati, and ossa unguis. 

The maxilla inferior, or lower jaw, which 
in its shape resembles a horse-shoe, consists 
of two distinct bones in the foetus ; but these 
unite together soon after birth, so as to form 

M 



90 Osteology. 

only one bone. The upper edge of this bone, 
like the os maxillare superius, has an alveolar 
process, furnished with sockets for the teeth. 

On each side the posterior part of the bone 
rises almost perpendicularly into two process- 
es. The highest of these, called the coronoid 
process, is pointed .-and thin, and serves for 
the insertion of the temporal muscle. The 
other, or condyloid process, as it is called, is 
shorter and thicker, and ends in an oblong 
rounded head, which is received into a fossa 
of the temporal bone, and is formed for a 
moveable articulation with the cranium. This 
joint is furnished with a moveable cartilage. 
At the bottom of each coronoid process, on 
its inner part, we observe a foramen extend- 
ing under the roots of all the teeth, and ter- 
minating at the outer surface of the bone near 
the chin. Each of these canals transmits an 
artery, vein, and nerve, from which branches 
are sent off to the teeth. 

The lower jaw is capable of a great variety 
of motion. By sliding the condyles from the 
cavity towards the eminences on each side, 
we bring it horizontally forwards, as in biting; 
or we may bring the condyles only forward, 
and tilt the rest of the jaw backward, as in 
opening the mouth. We are likewise able to 
slide the condyles alternately backwards and 
forwards from the cavity to the eminence, and 
vice versa, as in grinding the teeth. The car- 
tilages, by adapting themselves to the differ- 
ent inequalities in these several motions of the 



Osteology, 91 

jaw, serve to secure the articulation, and to 
prevent any injuries from friction. 

The alveolar processes are composed of an 
outer and inner bony plate, united together by 
thin partitions, which at the fore part of the 
jaw divide the processes into as many sockets 
as there are teeth. But at the back part of 
the jaw, where the teeth have more than one 
root, we find a distinct cell for each root. In 
both jaws these processes begin to be formed 
with the teeth ; they likewise accompany them 
in their growth, and gradually disappear when 
the teeth are removed. 



3. Of the Teeth. 

The teeth are bones of a particular struc- 
ture, formed for the purposes of mastication 
and the articulation of the voice. It will be 
necessary to consider their composition and fi- 
gure, their number and arrangement, and the 
time and order in which they appear. 

In each tooth we may distinguish a body, a 
neck, and a root or fangs. 

The body of the tooth is that part which 
appears above the gums. The root is fixed 
into the socket, and the neck is the middle 
part between the two. 

The teeth are composed of two substances, 
viz. enamel and bone. The enamel, or the 
vitreous or cortical part of the tooth, is a 
white and very hard and compact substance 
peculiar to the teeth, and appears fibrous o-r 



92 Osteology. 

striated when broken. This substance is thick- 
est on the grinding surface, and becoming gra- 
dually thinner, terminates insensibly at the 
necK of the tooth. Ruysch * affirmed, that he 
could trace the arteries into the hardest part 
of the teeth; Liewenhoeckf suspected the fibres 
of the enamel to be so many vessels ; and 
Monro % says, he has frequently injected the 
vessels of the teeth in children, so as to 
make the inside of the cortex appear perfectly 
red. But it is certain, that it is not tinged by 
a madder diet, and that no injection will ever 
reach it, so that it has no appearance of be- 
ing vascular \. 

The bony part, which composes the inner 
substance of the body, neck, and root of tho 
tooth, resembles other bones in its structure, 
but it is much harder than the most compact 
part of bones in general. As a tooth when 
once formed receives no tinge from a madder 
diet, and as the minutest injections do not pe- 
netrate into its substance, this part of the 
tooth has, like the enamel, been supposed not 
to be vascular. But when we consider that 
the fangs of a tooth are invested by a perios- 
teum, and that the swellings of these fangs 
are analogous to the swellings of other bones, 
we may reasonably conclude, that there is a 
similarity of structure ; and that this bony 
part has a circulation through its substance, 

* Thefadr to no. 27. 
f Arcan. Natur continuat. Epiftol. 
% Anat of the Human Bones. 
j Hunter on the Teeth. 



Osteology. 93 

although from its hardness we are unable to 
demonstrate its vessels. 

In each tooth we find an inner cavity, into 
which enter an artery, vein, and nerve. This 
cavity begins by a small opening, and becom- 
ing larger, terminates in the body of the tooth. 
In advanced life this hole sometimes closes, 
and the tooth is of course rendered insensible. 

The periosteum surrounds the teeth from 
their fangs to a little beyond their bony sock- 
ets, where we find it adhering to the gums. 
This membrane, while it incloses the teeth, 
serves at the same time to line the sockets, so 
that it may be considered as common to both. 

The teeth are likewise secured in their sock- 
ets by means of the gums ; a red, vascular, 
firm, and elastic substance, that possesses but 
little sensibility. In the gums of infants we 
find a hard ridge extending through their 
whole length, but no such ridge is to be seen 
in old people who have lost their teeth. 

The number of the teeth in both jaws at full 
maturity, usually varies from twenty-eight to 
thirty-two. They are commonly divided into 
three classes, viz. incisores, canini, and grind- 
ers or molares.* The incisores are the four 
teeth in the fore part of each jaw. They 
have each of them two surfaces ; one anterior 

* Mr. Hunter has thought proper to vary this division. He 
retains the old name of incisores to the four fore teeth, but he 
distinguishes the canine teeth by the name of the cuspinati. The 
two teeth •'which are next to these, and which have been usu- 
ally ranked with the molares, he calls the bicuspides ; and he 
gives the name of grinders only to the three last teeth on, each 
side. 



94 Osteology. 

and convex, the other posterior and slightly 
concave, both of which terminate in a sharp 
edge. They are called incisor es from their 
use in dividing the food. They are usually 
broader and thicker in the upper than in the 
under jaw; and, by being placed somewhat 
obliquely, generally fall over the latter. 

The canini derive their name from their re- 
semblance to a dog's tusks, being the longest 
of all the teeth. We find one on each side 
of the incisores, so that there are two canini 
in each jaw. Their fang resembles that of the 
incisores, but is much larger; and in their 
shape they appear like an incisor with its edge 
worn off, so as to terminate in a narrow point. 

These teeth not being calculated for cutting 
and dividing the food like the incisores, or for 
grinding it like the molares, seem to be intend- 
ed for laying hold of substances.* 

The molares or grinders, of which there 
are ten in each jaw, are so called, because 
from their shape and size they are fitted for 
grinding the food. Each of the incisores and 
canini is furnished only with one fang ; but in 
the molares of the under jaw we constantly 
find two fangs, and in those of the upper jaw 
three fangs. These fangs are sometimes se- 
parated into two points, and each of these points 
has sometimes been described as a distinct 
fang. 

* Mr. Hunter remarks of these teeth, that we may trace in 
them a similiarity in shape, situation, and use, from the most 
imperfectly carnivorous animal, which we believe to be the hu- 
man species, to xhz lion, which is the most perfectly carnivo- 
rous. 



Osteology. 95 

The two first of the molares, or those near- 
est to the canine teeth on each side, differ 
from the other three, and are with great pro* 
priety named bicuspides by Mr. Hunter. They 
have sometimes only one root, and seem to be 
of a middle nature between the incisores and 
the larger molares. The two next are much 
larger. The fifth or last grinder on each side 
is smaller and shorter than the rest ; and from 
its not cutting the gum till after the age of 
twenty, and sometimes not till much later in 
life, is called dens sapientite. 

There is in the structure and arrangement 
of all these teeth an art which cannot be suf- 
ficiently admired. To understand it properly, 
it will be necessary to consider the under jaw 
as a kind of lever, with its fixed points at its 
articulations with the temporal bones: — it will 
be right to observe, too, that its powers arise 
from its different muscles, but in elevation 
chiefly from the temporalis and masseter ; and 
that the aliment constitutes the object of re- 
sistance. It will appear, then, that the mola- 
res, by being placed nearest the centre of mo- 
tion, are calculated to press with a much 
greater force than the other teeth, independent 
of their grinding powers which they possess 
by means of the pterygoid muscles ; and that 
it is for this reason we put between them any 
hard body we wish to break. 

The canini and incisores are placed farther 
from this point, and of course cannot exert so 
much force ; but they are made for cutting 
and tearing the food, and this form seems to 
make amends for their deficiency in strength. 



96 Osteology. 

There are examples of children who have 
come into the world with two, three, and even 
four teeth; but these examples are very rare; 
and it is seldom before the seventh, eighth, 
or ninth month after birth, that the incisores, 
which are the first formed, begin to pass 
through the gum. The symptoms of denti- 
tion, however, in consequence of irritation 
from the teeth, frequently take place in the 
fourth or fifth month. — About the twentieth 
or twenty-fourth month, the canini and two 
molares make their appearance. 

The dangerous symptoms that sometimes 
accompany dentition, are owing to the pres- 
sure of the teeth on the gum, which they ir- 
ritate so as to excite pain and inflammation. 
This irritation seems to occasion a gradual 
wasting of the gum at the part, till at length 
the tooth makes its appearance. 

The symptoms are more or less alarming, in 
proportion to the resistance which the gum 
affords to the teeth, and according to the num- 
ber of teeth which may chance to seek a pas- 
sage at the same time. Were they all to ap- 
pear at once, children would fall victims to 
the pain and excessive irritation ; but Nature 
has so very wisely disposed them, that they 
usually appear one after the other, with some 
distance of time between each. The first in- 
cisor that appears is generally in the lower 
jaw, and is followed by one in the upper jaw. 
Sometimes the canini, but more commonly one 
of the molares, begins to pass through the 
gum first. 



Osteology. 97 

These 20 teeth, viz. eight incisores, four 
canini, and eight molares, are called tempora- 
ry or milk teeth, because they are all shed be- 
tween tiie age of seven and fourteen, and are 
succeeded by what are called the permanent or 
adult teeth. The latter are of a firmer texture, 
and have larger fangs. 

These adult teeth being placed in a distinct 
set of alveoli, the upper sockets gradually dis- 
appear, as the under ones increase in size, till 
at length the temporary, or upper teeth, hav- 
ing no longer any support, consequently fall 
out. 

To these 20 teeth, which succeed the tem- 
porary ones, 12 others are afterwards added, 
viz. three molares on each side in both jaws: 
and in order to make room for this addition, 
we find that the jaws gradually lengthen in 
proportion to the growth of the teeth ; so that 
with 20 teeth, they seem to be as completely 
filled as they are afterwards with 32. This is 
the reason why the face is rounder and flatter 
in children than in adults. 

With regard to the formation of the teeth, 
we may observe, that in a foetus of four months, 
the alveolar process appears only as a shallow 
longitudinal groove, divided by minute ridges 
into a number of intermediate depressions ; in 
each of which we find a small pulpy substance 
surrounded by a vascular membrane. This 
pulp gradually ossifies, and its lower part is 
lengthened out to form the fang. When the 
bony part of the tooth is formed, its surface 
begins to be intrusted with the enamel. How 

N 



98 Osteology. 

the latter is formed and deposited, we are not 
yet able to determine. 

The rudiments of some of the adult teeth 
begin to be formed at a very early period, for 
the pulp of one of the ineisores may general- 
ly be perceived in a fcetus of eight months, 
and the ossification begins in it soon after birth. 
The first bicuspis begins to ossify about the 
fifth or sixth, and the second about the seventh 
year. The first adult grinder cuts the gum 
about the 12th, the second about the 18th, and 
the third, or dens sapiential, usually between 
the 20th and 30th year. 

The teeth, like other bones, are liable to be 
affected by disease. Their removal is like- 
wise the natural consequences of old age ; for 
as we advance in life, the alveoli fill up, 
and the teeth, especially the ineisores, fall out. 
When this happens, the chin projects forward, 
and the face is much shortened. 



4. Of the Os Hyoides. 



* 



The os hyoides, which is placed at the root 
of the tongue, was so called by the ancients 
on account of its supposed resemblance to 
the Greek letter v. 



* This boric is very seldom preserved with the skeleton, and 
cannot be included among the bones of the head, or any other 
division of the skeleton Thomas Bartholin has perhaps very 
properly described it among parts contained in the mouth ; but 
the generality of anatomical writers have placed it, as it is here, 
after the bones of the face. 



Osteology. 99 

It will be necessary to distinguish in it, its 
body, horns, and appendices. 

The body, which is the middle and broad- 
est part of the bone, is so placed that it may 
be easily felt at the fore part of the throat. 
Anteriorly it is irregularly convex, and its in- 
ner surface is unequally concave. Its cornua, 
or horns, which are flat and a little bent, be- 
ing much longer than the body part, may be 
described as forming the sides of the », The 
appendices, or little horns, as they are called 
by M. Windslow, and some other writers, are 
two processes which rise up from the articu- 
lations of the cornua with the body, and are 
usually connected with the styloid process on 
each side by means of a ligament. 

The uses of this bone are to support the 
tongue, and afford attachment to a great num- 
ber of muscles ; some of which perform the 
motions of the tongue, while others act on 
the larynx and fauces. 

Sect. III. Of the Bones of the Trunk. 

The trunk of the skeleton consists of the 
spine, the thorax, and the pelvis. 

1. Of the Spine. 

The spine is composed of a great number 
of bones called vertebra?, forming a long bo- 
ny column, in figure not much unlike the let- 
ter/. This column, which extends from the 



100 Osteology, 

head to the lower part of the body, may be 
said to consist of two irregular and unequal 
pyramids, united to each other in that part of 
tne loins where the last lumbar vertebra joins 
the os sacrum. 

The vertebra: of the upper and longest py- 
ramid are called true vertebra 7 , in contradis- 
tinction to those of the lowermost pyramid, 
which, from their being immoveable in the 
adult, are styled false vertebra. It is upon 
the bones of the spine that the body turns ; 
and it is to this circumstance they owe their 
name, which is derived from the Latin verb 
vertere, to turnafasx. Medical VMvgv 

The true vertebra? are divided into three 
classes of cervical, dorsal and lumbar verte- 
bra?. — The false vertebra? consist of the os sa- 
crum and os coccygis. 

In each vertebra, as in other bones, it will 
be necessary to remark the body of the bone, 
its processes, and cavities. 

The body, which is convex before, and 
concave behind, where it assists in forming 
the cavity of the spine, may be compared 
to part of a cylinder cut off transversely. 

Each vertebra affords seven processes. 
The first is at the back part of the vertebra, 
and from its shape and direction is named the 
spinous process. On each side of this are two 
others, which, from their situation with re- 
spect to the spine, are called transverse pro- 
cesses. The four others are styled oblique or 
articular processes. They are much smaller 
than the spinous or transverse ones. Two of 



Osteology. 101 

them are placed on the upper, and two on the 
lower part of each vertebra, rising from near 
the basis of each transverse process. They 
have gotten the name of oblique processes, from 
their situation with respect to the processes 
with which they are articulated ; and they are 
sometimes styled articular processes, from the 
manner in which they are articulated with 
each other; the two superior processes of one 
vertebra being articulated with the two infe- 
rior processes of the vertebra above it. Each 
of these processes is covered with cartilage 
at its articulation, and their articulations with 
each other are by a species of ginglimus. 

In each vertebra, between its body and its 
processes, we find a hole large enough to ad- 
mit a finger. These holes or foramina, corre- 
spond with each other through all the vertebra?, 
and form the long bony channel in which the 
spinal marrow is placed. We may likewise 
observe four notches in each vertebra. Two 
of tliese notches are at the upper, and two 
at the lower part of the bone, between the 
oblique processes and the body of the ver- 
tebra. Each of these notches meeting with a 
similar opening in the vertebra above or be- 
low it, forms a foramen for the passage of 
blood-vessels, and of the nerves out of the 

spine. 

The bones of the spine are united toge- 
ther by means of a substance, which in young 
subjects appears to be of a ligamentous, but 
in adults more of a cartilaginous nature. This 
intervertebral substance, which forms a kind 



102 Osteology. 

of partition between the several vertebra?, is 
thicker and more flexible between the lumbar 
vertebras than in the other parts of the spine, the 
most considerable motions of the trunk being- 
performed on those vertebrae. This substance 
being very elastic, the extension and flexion 
of the body, and its motion backwards and 
forwards, or to either side, are performed with 
great facility. This elasticity seems to be the 
reason why people who have been long stand- 
ing, or have carried a considerable weight, 
are found to be shorter than when they have 
been long in bed. In the two first instances 
the intervertebral cartilages (as they are usu- 
ally called) are evidently more exposed to 
compression than when we are in bed in an 
horizontal posture. 

In advanced life these cartilages become 
shrivelled, and of course lose much of their 
elasticity. This may serve to account for the 
decrease in stature and the stooping forward 
which are usually to be observed in old peo- 
ple. 

Besides the connection of the several verte- 
brae by means of this intervertebral substance, 
there are likewise many strong ligaments, both 
external and internal, which unite the bones 
of the spine to each other. Their union is al- 
so strengthened by a variety of strong muscles 
that cover and surround the spine. 

The bones of the spine are found to dimi- 
nish in density, and to be less firm in their 
texture in proportion as they increase in bulk ; 
so that the lowermost vertebrae, though the 



Osteology. 103 

largest, are not so heavy in proportion as the 
upper ones. By this means the size of these 
bones is increased without adding to their 
weight : a circumstance of no little importance 
in a part like the spine, which, besides flexi- 
bility and suppleness, seems to require light- 
ness as one of its essential properties. 

In very young children, each vertebra con- 
sists of tiiree bony pieces united by cartilages 
which afterwards ossify. 

There are seven vertebrae of the neck — 
they are of a firmer texture than the other 
bones of the spine. Their transverse process- 
es are forked for the lodgment of muscles, 
and at the bottom of each we observe a fora- 
men, through which pass the cervical artery 
and vein. The first and second of these ver- 
tebrae must be described more particularly. 
The first approaches almost to an oval shape 
— On its superior surface it has two cavities 
which admit the condyles of the occipital 
bone with which it is articulated. This verte- 
bra, which is called atlas from its supporting 
the head, cannot well be described as having 
either body or spinous process, being a kind 
of bony ring. Anteriorly, where it is articu- 
lated to the odontoid process of the second 
vertebra, it is very thin. On its upper surface 
it has two cavities which admit the condyles 
of the occipital bone. By this connection the 
head is allowed to move forwards and back- 
wards, but has very little motion in any other 
direction. 



104 Osteology. 

The second vertebra has gotten the name of 
dentata, from its having, at its upper and an- 
terior part, a process called the odontoid or 
tooth-like process, which is articulated with the 
atlas, to which this second vertebra may be 
said to serve as an axis. This odontoid pro- 
cess is of a cylindrical shape, somewhat flat- 
tened, however, anteriorly and posteriorly. At 
its fore-part where it is received by the atlas, 
we may observe a smooth, convex, articulat- 
ing surface. It is by means of this articula- 
tion that the head performs its rotatory motion, 
the atlas in that case moving upon this odon- 
toid process as upon a pivot. But when this 
motion is in any considerable degree, or, in 
other words, when the head moves much ei- 
ther to the right or left, all the cervical verte- 
brae seem to assist, otherwise the spinal mar- 
row would be in danger of being divided trans- 
versely by the first vertebra. 

The spinous process of each of the cervi- 
cal vertebrae is shorter, and their articular pro- 
cesses more oblique, than in the other bones 
of the spine. 

These 12 vertebrae are of a middle size be- 
tween those of the neck and loins. At their 
sides we may observe two depressions, one at 
the upper and the other at the lower part of 
the body of each vertebra:; which uniting with 
similar depressions in the vertebrae above and 
below, form articulating surfaces, covered with 
cartilages, for receiving the heads of the ribs ; 
and at the fore-part of their transverse process 



Osteology. 105 

(excepting the two last) we find an articulating 
surface tor receiving the tuberosity of the ribs* 

These five vertebras differ only from those 
of the back in their being larger, and in hav- 
ing their spinous processes at a greater dis- 
tance from each other. The most consider- 
able motions of the trunk are made on these 
vertebrae; and these motions could not be per- 
formed with so much ease, were the process- 
es placed nearer to each other. 

The os sacrum, which is composed of five 
or six pieces in young subjects, becomes one 
bone in more advanced age. 

It is nearly of a triangular figure, its infe- 
rior portion being bent a little forwards. Its 
superior part has two oblique processes which 
are articulated with the last of the lumbar ver- 
tebra? ; and it has likewise commonly three 
small spinous processes, which gradually be- 
come snorter, so that the lowermost is not so 
long as the second, nor the second as the up- 
permost. Its transverse processes are formed 
into one oblong process, which becomes gra- 
dually smaller as it descends. Its concave or 
anterior side is usually smooth, but its poste- 
rior convex side has many prominences (the 
most remarkable of which are the spinous pro- 
cesses just now mentioned,) which are filled 
up and covered with the muscular and tendi- 
nous parts behind. 

This bone has five pair of holes, which af- 
ford a passage to blood-vessels, and likewise 
to the nerves that are derived from the spinal 
marrow, which is continued even here, being 

O 



10 G Osteology. 

lodged in a triangular cavity, that becomes 
smaller as it descends, and at length termi- 
nates obliquely at the lower part of this bone. 
Below the third division of the os sacrum, this 
canal is not completely bony as in the rest of 
the spine, being secured at its back part only 
by a very strong membrane, so that a wound 
at this part must be extremely dangerous. 

The os sacrum is united laterally to the os- 
sa innominata or hip-bones, and below to the 
coccyx. 

The coccyx, which, like the os sacrum, is 
in young peopie made up of three or four dis- 
tinct parts, usually becomes one bone in the 
adult state. 

It serves to support the intestinum rectum ; 
and, by its being capable of some degree of 
motion at its articulation with the sacrum, and 
being like that bone bent forwards, we are en- 
abled to sit with ease. 

This bone is nearly of a triangular shape, 
being broadest at its upper part, and from 
thence growing narrower to its apex, ' where it 
is not bigger than the little finger. 

It has got its name from its supposed re- 
semblance to a cuckow's beak. It differs 
greatly from the vertebras, being commonly 
without any processes, and having no cavity 
for the spinal marrow, or foramina for the 
transmission of nerves. 

The spine, of which we have now finished 
the anatomical description, is destined for ma- 
ny great and important uses. The medulla 
spinalis is lodged in its bony canal secure from 



Osteology. 107 

external injury. It serves as a defence to the 
abdominal and thoracic viscera, and at the 
same time supports the head, and gives a ge- 
neral firmness to the whole trunk. 

We have before compared it to the letter/, 
and its different turns will be found to render 
it not very unlike the figure of that letter. — 
In the neck we see it projecting somewhat for- 
ward to support the head, which without this 
assistance would require a great number of 
muscles. — Lower down, in the thorax, we find 
it taking a curved direction backwards, and of 
course increasing the cavity of the chest. Af- 
ter this, in the loins, it again projects forwards 
in a direction with the centre of gravity, by 
which means we are easily enabled to keep the 
body in an erect posture, for otherwise we 
should be lmble to fall forward. Towards its 
inferior extremity, however, it again recedes 
backward, and thus assists in forming the pel- 
vis, the name given to the cavity in which the 
urinary bladder, intestinum rectum, and other 
viscera are placed. 

If this bony column had been formed only 
of one piece, it would have been much more 
easily fractured than it is now : and by confin- 
ing the trunk to a stiff situation, a variety of 
motions would have been altogether prevent- 
ed, which are now performed with ease by the 
great number of bones of which it is compos- 
ed. 

It is firm, and yet to this firmness there is 
added a perfect flexibility. If it be required 
to carry a load upon the head, the neck be- 



108 Osteology. 

comes stiff with the assistance of its muscles, 
and accommodates itself to the load, as if it 
was composed only of one bone — In stooping 
likewise, or in turning to either side, the spine 
turns itself in every direction, as if all its 
bones were separated from each other. 

In a part of the body, like the spine, that 
is made up of so great a number of bones, 
and intended for such a variety of motion, 
there must be a greater danger of dislocation 
than fracture ; but we shall find, that this is 
very wisely guarded against in every direction 
by the processes belonging to each vertebra, 
and by the ligaments, cartilages, h.c. by which 
these bones are connected with each other. 



2. Of the Bones of the Thorax. 

The thorax, or chest, is composed of ma- 
ny bones, viz. the sternum which is placed at 
its anterior part, twelve ribs on each side 
which make up its lateral parts, and the dor- 
sal vertebras which constitute its posterior part. 
These last have been already described. 

The sternum is the long bone which ex- 
tends itself from the upper to the lower part 
of the breast anteriorly, and to which the ribs 
and the clavicles are articulated. 

In children it is composed of several bones 
united by cartilages ; but as we advance in life, 
most of these cartilages ossify, and the ster- 
num in the adult state is found to consist on- 



Osteology. 109 

ly of three pieces, and sometimes becomes one 
bone. It is however generally described as 
being composed of three parts — one superior, 
which is broad, thick, and short ; and one in 
the middle, which is thinner, narrower, and 
longer than the other. 

It terminates at its lower part by a third 
piece, which is called the xyphoid, or sword- 
like cartilage, from its supposed resemblance 
to the blade of a sword, and because in young 
subjects it is commonly in a cartilaginous state. 
We have already observed, that this bone 
is articulated with the clavicle on each side. 
It is likewise joined to the fourteen true ribs, 
viz. seven on its right and seven on its left 
side. 

The ribs are bones shaped like a bow, form- 
ing the sides of the chest. There are twelve 
on each side. They are distinguished into 
true and false ribs : The seven upper ribs 
which are articulated to the sternum are call- 
ed true ribs, and the five lower ones that are 
not immediately attached to that bone are call- 
ed false ribs. 

On the inferior and interior surface of each 
rib, we observe a sinuosity for the lodgment 
of an artery, vein, and nerve. 

The ribs are not bony through their whole 
length, their anterior part being cartilaginous. 
They are articulated with the vertebrae and 
sternum. Every rib (or at least the greater 
number of them) has at its posterior part two 
processes ; one at its extremity called the head 
of the rib, by means of which it is articulated 



110 Osteology. 

with the body of two vertebra? ; and another, 
called its tuberosity, by which it is articulated 
with the transverse process of the lowest of 
these two vertebra?. The first rib is not arti- 
culated by its extremity to two vertebra?, be- 
ing simply attached to the upper part of the 
first vertebra of the back. The seven superi- 
or or true ribs are articulated anteriorly with 
the sternum by their cartilages ; but the false 
ribs are supported in a different manner — the 
eighth, which is the first of these ribs, being 
attached by its cartilage to the seventh ; the 
ninth to the eighth, &c. 

The two lowermost ribs differ likewise from 
all the rest in the following particulars : they 
are articulated only with the body of the ver- 
tebra, and not with a transverse process ; and 
anteriorly, their cartilage is loose, not being 
attached to the cartilages of the other ribs; 
and this seems to be, because the most consi- 
derable motions of the trunk are not perform- 
ed on the lumbar vertebra? alone, but likewise 
on the two last vertebrae of the back ; so that 
if these two ribs had been confined at the fore 
part like the other ribs, and had been likewise 
articulated with the bodies of two vertebra?, 
and with the transverse processes, the moti- 
on of the two last vertebra?, and consequently 
of the whole trunk, would have been impeded. 

The ribs help to form the cavity of the tho- 
rax ; they afford attachment to different mus- 
cles ; they are useful in respiration ; and they 
serve as a security to the heart and lungs. 



Osteology. Ill 

3. Of the Bones of the Pelvis. 

The pelvis is composed of the os sacrum, 
os coccygis, and two ossa innominata. The 
two first of these bones were included in the 
account of the spine, to which they more pro- 
perly belong. 

In children, each os innominatum is com- 
posed of three distinct bones ; but as we ad- 
vance in life the intermediate cartilages gradu- 
ally ossify, and the marks of the original se- 
paration disappear, so that they become one 
irregular bone ; still however continuing to re- 
tain the names of ilium, ischium, and pubis, 
by which their divisions were originally dis- 
tinguished, and to be described as three dif- 
ferent bones by the generality of anatomists. 
The os ilium forms the upper and most consi- 
derable part of the bone, the os ischium its 
lower and posterior portion, and the os pubis 
its fore part. 

The os ilium or haunch bone, is articulated 
posteriorly to the os sacrum by a firm cartila- 
ginous substance, and is united to the os pu- 
bis before and to the os ischium below. Its 
superior portion is thin, and terminates in a 
ridge called the crista or spine of the ilium, 
and more commonly known by the name of the 
haunch. This crista rises up like an arch ; 
being turned somewhat outwards, so as to re- 
semble the wings of a phaeton. 

Externally this bone is unequally prominent 
and hollowed for the lodgment of muscles; in- 
ternally we find it smooth and concave. At 



112 Osteology. 

its lower part there is a considerable ridge on 
its inner surface. This ridge extends from 
the os sacrum, and corresponds with a similar 
prominence both on that bone and the ischi- 
um ; forms with the inner part of the ossa pu- 
bis what in midwifery is termed the brim of 
the pelvis. 

The crista or spine, which at first is an epi- 
physis, has two considerable tuberosities ; one 
anteriorly, and the other posteriorly, which is 
the largest of the two : these, from their pro- 
jecting more than the parts of the bone below 
them, have gotten the name of spinal process- 
es. From the anterior spinous process, the 
sartorius and tensor vaginas femoris muscles 
have their origin ; and below the posterior 
process we observe a considerable niche in 
the bone, which, in the recent subject, is 
formed into a large foramen, by means of a 
strong ligament that is stretched over its low- 
er part from the os sacrum to the sharp-point- 
ed process of the ischium. This hole affords 
a passage to the great sciatic nerve, and to the 
posterior crural vessels under the pyriform 
muscle, part of which likewise passes out 
here. 

The os ischium, or hip-bone, which is of 
a very irregular figure, constitutes the lower 
lateral parts of the pelvis, and is commonly 
divided into its body, tuberosity, and ramus. 
The body forms the lower and most consider- 
able portion of the acetabulum, and sends a 
sharp-pointed process backwards, called the 
spine of the ischium. To this process the li- 



Osteology. 113 

gament adheres, which was just now spoken 
of, as forming a foramen for the passage of 
the sciatic nerve. — The tuberosity, which is 
the lowest part of the trunk, and supports us 
when we sit, is large and irregular, affording 
origin to several muscles. From this tubero- 
sity we find the bone becoming thinner and 
narrower. This part, which has the name of 
ramus or branch, passes forwards and up- 
wards, and concurs with the ramus of the os 
pubis, to form a large hole called the foramen 
magnum ischii, or thyroideum, as it is some- 
times named, from its resemblance to a. (! door 
or shield. This hole, which in the recent 
subject is closed by a strong membrane called 
the obturator ligament, affords through its 
whole circumference attachment to muscles. 
At its upper part where we observe a niche 
in the bone, it gives passage to the obturator 
vessels and nerves, which go to the inner part 
of the thigh. Nature seems every where to 
avoid an unnecessary weight of bone, and 
this foramen, no doubt, serves to lighten the 
bones of the pelvis. 

The os pubis or share-bone, which with its 
fellow forms the fore-part of the pelvis, is the 
smallest division of the os innominatum. It 
is united to its fellow by means of a strong 
cartilage, which forms what is called the sym- 
physis pubis. 

In each os pubis we may distinguish the 
body of the bone, its angle, and ramus. The 
body or outer part is united to the os ilium. 
The angle comes forward to form the sym- 

P 



114 Osteology. 

physis, and the ramus is a thin process which 
unites with the ramus of the ischium, to form 
the foramen thyroideum. 

The three bones we have described as com- 
posing each os innominatum, all assist in form- 
ing the acetabulum, in which the head of the 
os femoris is received. 

This cavity is every where lined with a 
smooth cartilage, excepting at its inner part, 
where we may observe a little fossa, in which 
are lodged the mucilaginous glands of the joint. 
We may likewise notice the pit or depression 
made by the round ligament, as it is improper- 
ly called, which, by adhering to this cavity and 
to the head of the thigh-bone, helps to secure 
the latter in the socket. 

These bones, which are united to each 
other and to the spine by many very strong 
ligaments, serve to support the trunk, and to 
connect it with the lower extremities ; and at 
the same time to form the pelvis or bason, in 
which are lodged the intestines and urinary 
bladder, and in women the uterus ; so that the 
study of this part of osteology is of the utmost 
importance in midwifery. 

It is worthy of observation, that in women 
the os sacrum is usually shorter, broader, and 
more hollowed, the ossa ilia more expanded, 
and the inferior opening of the pelvis larger 
than in men. 

Sect. IV. Of the Extremities. 

These parts of the skeleton consist of the 
upper extremity and the lower. 



Osteology. 115 

1. Of the Upper Extremity. 



This consists of the shoulder, the arm, and 
the hand. 

1. Of the shoulder. 

The shoulder consists of two bones, the 
clavicula and the scapula. 

The former, which is so named from its re- 
semblance to the key in use amongst the an- 
cients, is a little curved at both its extremities 
like an italic/. It is likewise called jugulum^ 
or collar-bone, from its situation. It is about 
the size of the little finger, but longer, and be- 
ing of a very spongy substance is very liable 
to be fractured. In this, as in other long bones, 
we may distinguish a body and two extremi- 
ties. The body is rather flattened than round- 
ed. The anterior extremity is formed into 
a slightly convex head, which is nearly of a tri- 
angular shape. The inferior surface of the 
head is articulated with the sternum. The 
posterior extremity, which is flatter and broad- 
er than the other, is connected to a process 
of the scapula, called acromion. Both these 
articulations are secured by ligaments, and in 
that with the sternum we meet with a move- 
able cartilage, to prevent any injury from fric- 
tion. 

The clavicle serves to regulate the motions 
of the scapula, by preventing it from being 



116 Osteology. 

brought too much forwards, or carried too far 
backwards. It affords origin to several mus- 
cles, and helps to cover and protect the sub- 
clavian vessels, which derive their name from 
their situation under this bone. 

The scapula, or shoulder-blade, which is 
nearly of a triangular shape, is fixed to the 
posterior part of the true ribs, somewhat in 
the manner of a buckler. It is of a very un- 
equal thickness, and, like all other broad, flat 
bones, is somewhat cellular. Exteriorly it is 
convex, and interiorly concave, to accommo- 
date itself to the convexity of the ribs. We 
observe in this bone three unequal sides, which 
are thicker and stronger than the body of the 
bone, and are therefore termed its cost<z. The 
largest of the three, called also the basis, is 
turned towards the vertebrae. Another, which 
is less than the former, is below this ; and the 
third, which is the least of the three, is at 
the upper part of the bone. Externally the 
bone is elevated into a considerable spine, 
which rising small at the basis of the scapula, 
becomes gradually higher and broader, and 
divides the outer surface of the bone into two 
fossae. The superior of these, which is the 
smallest, serves to lodge the supra spinatus 
muscle ; and the inferior fossa, which is much 
larger than the other, gives origin to the infra 
spinatus. This spine terminates in a broad and 
flat process at the top of the shoulder, called 
the processus acromion, to which the clavicle is 
articulated. This process is hollowed at its 
lower part to allow a passage to the supra and 



Osteology. 117 

infra spinati muscles. The scapula has like- 
wise another considerable process at its upper 
part, which, from its resemblance to the beak 
of a bird, is called the coracoid process. From 
the outer side of this coracoid process, a strong 
ligament passes to the processus acromion, 
which prevents a luxation of the os humeri up- 
wards. A third process begins by a narrow 
neck, and ends in a cavity called glenoid, for 
the connection of the os humeri. 

The scapula is articulated with the clavicle 
and os humeri, to which last it serves as a ful- 
crum ; and by varying its position it affords a 
greater scope to the bones of the arm in their 
different motions. It likewise gives origin to 
several muscles, and posteriorly serves as a de- 
fence to the trunk. 

2. Bones of the Arm. 

The arm is commonly divided into two parts, 
which are articulated to each other at the el- 
bow. The upper part retains the name of arm, 
properly so called, and the lower part is usu- 
ally called the fore-arm. 

The arm is composed of a single bone call- 
ed os humeri. This bone, which is almost of 
a cylindrical shape, may be divided into its bo- 
dy and its extremities. 

The upper extremity begins by a large, 
round smooth head, which is admitted into the 
glenoid cavity of the scapula. On the upper 
and fore part of , the bone there is a groove 
for lodging the long head of the biceps mus- 



118 Osteology. 

cle of the arm ; and on each side of the groove, 
at the upper end of the bone, there is a tuber- 
cle to which the spinata muscles are fixed. 

The lower extremity has several processes 
and cavities. The principal processes are its 
two condyles, one exterior and the other inte- 
rior, and of these the last is the largest. Be- 
tween these two we observe two lateral protu- 
berances, which, together with a middle cavi- 
ty, form as it were a kind of pully upon which 
the motions of the fore-arm are chiefly per- 
formed At each side of the condyles, as well 
exteriorly as interiorly, there is another emi- 
nence which gives origin to several muscles of 
the hand and fingers. Posteriorly and superi- 
orly, speaking with respect to the condyles, we 
observe a deep fossa which receives a consi- 
derable process of the ulna ; and anteriorly and 
opposite to this fossa, we observe another, 
which is much less and receives another pro- 
cess of the same bone. 

The body of the bone has at its upper and 
anterior part a furrow which begins from be- 
hind the head of the bone, and serves to lodge 
the tendon of a muscle. The body of the os 
humeri is hollow through its whole length, and, 
like all other long bones, has its marrow. 

This bone is articulated at its upper part to 
the scapula. This articulation, which allows 
motion every way, is surrounded by a capsu- 
lar ligament ; that is sometimes torn in luxa- 
tion, and becomes an obstacle to the easy re- 
duction of the bone. Its lower extremity is 
articulated with the bones of the fore-arm. 



Osteology. 119 

The fore-arm is composed of two bones, the 
ulna and radius. 

The ulna or elbow-bone is much less than 
the os humeri, and becomes gradually small- 
er as it descends to the wrist. At its upper 
part it has two processes and two cavities. Of 
the two processes, the largest, which is situ- 
ated posteriorly, and called the olecranon, is 
admitted into the posterior fossa of the os hu- 
meri. The other process is placed anteriorly, 
and is called the coronoid process. In bending 
the arm it enters into the anterior fossa of the 
os humeri. This process being much smaller 
than the other, permits the fore -arm to bend 
inwards ; whereas the olecranon, which is 
shaped like a hook, reaches the bottom of its 
fossa in the os humeri as soon as the arm be- 
comes straight, and will not permit the fore- 
arm to be bent backwards. The ligaments 
likewise oppose this motion. 

Between the two processes we have describ- 
ed, there is a considerable cavity called the 
sygmoid cavity, divided into two fossa: by a 
small eminence, which passes from one pro- 
cess to the other; it is by means of this cavity 
and the two processes, that the ulna is articu- 
lated with the os humeri by gingiimus. 

At the bottom of the coronoid process interi- 
orly, there is a small sygmoid cavity, which 
serves for the articulation of the ulna with the 
radius. 

The body of the ulna is of a triangular 
shape : Its lower extremity terminates by a 
small 'head and a little styloid process. The 



12© Osteology. 

ulna is articulated above to the os humeri — 
both above and below to the radius, and to 
the wrist at its lower extremity. All these ar- 
ticulations are secured by means of ligaments. 
The chief use of this bone seems to be to sup- 
port and regulate the motions of the radius. 

The radius, which is so named from its sup- 
posed resemblance to the spoke of a wheel, is 
placed at the inside of the fore-arm. It is 
somewhat larger than the ulna, but not quite 
so long as that bone. Its upper part is cylin- 
drical, hollowed superiorly to receive the out- 
er condyle of the os humeri. Laterally it is 
admitted into the little sygmoid cavity of the 
ulna, and the cylindrical part of the bone turns 
in this cavity in the motions of pronation and 
supination.* This bone follows the ulna in 
flexion and extension, and may likewise be 
moved round its axis in any direction. The 
lower extremity of the radius is much larger 
and stronger than its upper part ; the ulna, on 
the contrary, is smaller and weaker below than 
above ; so that they serve to supply each other's 
deficiencies in both those parts. 

On the external side of this bone, we ob- 
serve a small cavity which is destined to re- 
ceive the lower end of the ulna ; and its low- 
er extremity is formed into a large cavity, by 
means of which it is articulated with the bones 

* The motions of pronation and supination may be easily 
described. If the palm of the hand, for instance, is placed on 
the surface of a table, the hand may be said to be in a state of 
pronation ; but if the back part of the hand is turned towards 
the table, the hand will be then in a state of supination. 



Osteology. 121 

of the wrist, and on this account it is some- 
times called manubrium manus. It supports 
the two first bones of the wrist on the side of 
the thumb, whereas the ulna is articulated with 
that bone of the wrist which corresponds with 
the little finger. 

Through the whole length both of this bone 
and the ulna, a ridge is observed, which affords 
attachment to an interosseous ligament. This 
ligament fills up the space between the two 
bones. 

3. Bones of the Hand. 

The carpus or wrist consists of eight small 
bones of an irregular shape, and disposed in two 
unequal rows. Those of the upper row are 
articulated with the bones of the fore-arm, and 
those of the lower one with the metacarpus. 

The ancient anatomists described these 
bones numerically; Lyserus seems to have 
been the first who gave to each of them a par- 
ticular name. The names he adopted are 
founded on the figure of the bones, and are 
now pretty generally received, except the first, 
which instead of M »x H //u (the name given to it 
by Lyserus, on account of its sinus that ad- 
mits a part of .the os magnum), has by later 
writers been named Scaphoides or Naviculare. 
This, which is the outermost of the upper row 
(considering the thumb as the outer side of 
the hand), is articulated with the radius; on 
its inner side it is connected with the os lu- 
nare, and below to the trapezium and trape- 

Q 



122 Osteology. 

zoides. Next to this is a smaller bone, called 
the os huiare: because its outer side, which 
is connected with the scaphoides, is shaped 
like a crescent. This is likewise articulated 
with the radius. On its inner side it joins the 
os cuneiforme, and anteriorly, the os magnum 
and os unciforme. 

The os cuneiforme, which is the third bone 
in the upper row, is compared to a wedge, 
from its being broader above, at the back of 
the hand, than it is below. Posteriorly it is 
articulated with the ulna, and anteriorly with 
the os unciforme. 

These three bones form an oblong articulat- 
ing surface, covered by cartilage, by which 
the hand is connected with the fore-arm. 

The os pisiforme, or pea-like bone, which 
is smaller than the three just now described, 
though generally classed with the bones of the 
upper row, does not properly belong to either 
series, being placed on the under surface of 
the os cuneiforme, so as to project into the 
palm of the hand. The four bones of the se- 
cond row correspond with the bones of the 
thumb and fingers ; the first, second, and 
fourth, are from their shapes named trapezi- 
um, trapezoides, and unciforme ; the third, from 
its being the largest bone of the carpus, is styl- 
ed os magnum. 

All these bones are convex towards the back, 
and slightly concave towards the palm of the 
hand ; their articulating surfaces are covered 
with cartilages, and secured by many strong 
ligaments, particularly by two ligamentous ex- 



Osteology. 125 

pansions, called the external and internal an- 
nular ligaments of the wrist. The former ex- 
tends in an oblique direction from the os pisi- 
forme to the styloid process of the radius, and 
is an inch and an half in breadth ; the latter or 
internal annular ligament is stretched from the 
os pisiforme and os unciforme, to the os sca- 
phoides and trapezium. These annular liga- 
ments likewise serve to bind down the tendons 
of the wrist and fingers. 

The metacarpus consists of four bones, 
which support the fingers ; externally they are 
a little convex, and internally somewhat con- 
cave, where they form the palm of the hand. 
They are hollow and of a cylindrical shape. 

At each extremity they are a little hollow- 
ed for their articulation ; superiorly with the 
bones of the carpus, and inferiorly with the 
first phalanx of the fingers, in the same man- 
ner as the several phalanges of the fingers 
are articulated with each other. 

The five fingers of each hand are composed 
of fifteen bones, disposed in three ranks call- 
ed phalanges : the bones of the first phalanx, 
which are articulated with the metacarpus, are 
the largest, and those of the last phalanx the 
smallest. All these bones are larger at their 
extremities than in their middle part. 

We observe at the extremities of the bones 
of the carpus, metacarpus, and fingers, seve- 
ral inequalities that serve for their articulation 
with each other; and these articulations are 
strengthened by means of the ligaments which 
surround them. 



124 Osteology. 

It will be easily understood that this multi- 
plicity of bones in the hand (for there are 27 
in each hand) is essential to the different mo- 
tions we wish to perform. If each finger was 
composed only of one bone instead ol three, 
it would be impossible for us to grasp any 
thing. 

2. Of the Lower Extremities. 

Each lower extremity is divided into four 
parts, viz. the os femoris, or thigh bone : the 
rotula, or knee pan ; the leg and the foot. 

1. Of the Thigh. 

The thigh is composed only of this bone, 
which is the largest and strongest we have. 
It will be necessary to distinguish its body and 
extremities: its body, which is of a cylindri- 
cal shape, is convex before and concave be- 
hind, where it serves to lodge several muscles. 

Throughout two-thirds of its length we ob- 
serve a ridge called line a aspera, which origi- 
nates from the trochanters, and after running 
for some way downwards, divides into two 
branches, that terminate in the tuberosities at 
the lower extremity of the bone. 

At its upper extremity we must describe the 
neck and smooth head of the bone, and like- 
wise two considerable processes : the head, 
which forms the greater portion of a sphere 
unequally divided, is turned inwards, and re- 
ceived into the great cotyloid cavity of the os 



Osteology. 125 

innominatum. At this part of the bone there is a 
little fossa to be observed, to which the round 
ligament is attached, and which we have al- 
ready described as tending to secure the head 
of this bone in the great acetabulum. The 
neck is almost horizontal, considered with re- 
spect to its situation with the body of the bone. 
Of the two processes, the external one, which 
is the largest, is called trochanter major ; and 
the other, which is placed on the inside of the 
bone, trochanter minor. They both afford at- 
tachment to muscles. The articulation of the 
os femoris with the trunk is strengthened by 
means of a capsular ligament, which adheres 
every where round the edge of the great co- 
tyloid cavity of the os innominatum, and sur- 
rounds the head of the bone. 

The os femoris moves upon the trunk in 
every direction. 

At the lower extremity of the bone are two 
processes called the condyles, and an interme- 
diate smooth cavity, by means of which it is 
articulated with the leg by ginglimus. 

All round the under end of the bone there 
is an irregular surface where the capsular li- 
gament of the joint has its origin, and where 
blood-vessels go into the substance of the 
bone. 

Between the condyles there is a cavity pos- 
teriorly, in which the blood-vessels and nerves 
are placed, secure from the compression to 
which they would otherwise be exposed in 
the action of bending the leg, and which would 
not fail to be hurtful. 



126 Osteology. 

At the side of each condyle externally, there 
is a tuberosity, from whence the lateral liga- 
ments originate, which are extended down to 
the tibia. 

A ligament likewise arises from each con- 
dyle posteriorly. One of these ligaments 
passes from the right to the left, and the other 
from the left to the right, so that they inter- 
Sect each other, and for that reason are called 
the cross ligaments. 

The lateral ligaments prevent the motion of 
the leg upon the thigh to the right or left ; and 
the cross ligaments, which are also attached 
to the tibia, prevent the latter from being 
brought forwards. 

In new-born children all the processes of 
this bone are cartilaginous. 

2. The Rotula, or Knee-pan. 

The rotula, patella, or knee-pan, as it is 
differently called, is a flat bone about four or 
five inches in circumference, and is placed at 
the fore-part of the joint of the knee. In its 
shape it is somewhat like the common figure 
of the heart, with its point downwards. 

It is thinner at its edge than in its middle 
part ; at its fore-part it is smooth and some- 
what convex ; its posterior surface, which is 
more unequal, affords an elevation in the mid- 
dle which is admitted between the two con- 
dyles of the os femoris. 

This bone is retained in its proper situation 
by a strong ligament which every where sur- 



Osteology, 127 

rounds it, and adheres both to the tibia and os 
femoris ; it is likewise firmly connected with 
the tibia by means of a strong tendinous liga- 
ment of an inch in breadth, and upwards of 
two inches in length, which adheres to the 
lower part of the patella, and to the tubero- 
sity at the upper end of the tibia. On account 
of this connection, it is very properly consi- 
dered as an appendage to the tibia, which it 
follows in all its motions, so as be to it what 
the olecranon is to the ulna. There is this 
difference, however, that the olecranon is a 
fixed process ; whereas the patella is movea- 
ble, being capable of sliding from above down- 
wards and from below upwards. This mobi- 
lity is essential to the rotatory motion of the 
leg. 

In very young children this bone is entirely- 
cartilaginous. 

The principal use of the patella seems to 
be to defend the articulation of the knee from 
external injury; it likewise tends to increase 
the power of the extensor muscles of the leg, 
by removing their direction farther from the 
centre of motion in the manner of a pulley. 

3. Of the Leg. 

The leg is composed of two bones : of these 
the inner one, which is the largest, is called 
tibia ; the other is much smaller, and named 
fibula. 

The tibia, which is so called from its re- 
semblance to the musical pipe of the ancients, 



128 Osteology. 

has three surfaces, and is not very unlike a 
triangular prism. Its posterior surface is the 
broadest; anteriorly it has a considerable 
ridge called the shin, between which and the 
skin there are no muscles. At the upper ex- 
tremity of this bone are two surfaces, a little 
concave, and separated from each other by an 
intermediate elevation. The two little cavities 
receive the condyles of the os femoris, and 
the eminence between them is admitted into 
the cavity which we spoke of as being be- 
tween the two condyles ; so that this articula- 
tion affords a specimen of the complete gin- 
glimus. Under the external edge of the up- 
per end of this bone is a circular flat surface, 
which receives the head of the fibula. 

At the lower and inner portion of the tibia, 
we observe a considerable process called mal- 
leolus interims. The basis of the bone termi- 
nates in a large transverse cavity, by which it 
is articulated with the uppermost bone of the 
foot. It has likewise another cavity at its low- 
er end and outer side, which is somewhat ob- 
long, and receives the lower end of the fibula. 

The tibia is hollow through its whole length. 

The fibula is a small long bone situated on 
the outside of the tibia. Its superior extremi- 
ty does not reach quite so high as the upper 
part of the tibia, but its lower end descends 
somewhat lower. Both above and below, it 
is articulated with the tibia by means of the 
lateral cavities we noticed in our description 
of that bone. 



Osteology. 129 

Its lower extremity is stretched out into a 
coronoid process, which is flattened at its in- 
side, and is convex externally, forming what 
is called the malleolus externus or outer ankle. 
This is rather lower than the malleolus inter- 
nals of the tibia. 

The body of this bone, which is irregularly 
triangular, is a little hollow at its internal sur- 
face, which is turned towards the tibia ; and it 
affords like that bone, through its whole length, 
attachment to a ligament, which from its situa- 
tion is called the interosseous ligament. 

4. Of the Foot. 

The foot consists of the tarsus, metatarsus, 
and toes. 

The tarsus is composed of seven bones, viz. 
the astragalus, os calcis, os naviculare, os cu- 
boides, and three others called cuneiform 
bones. 

The astragalus is a large bone with which 
both the tibia and fibula are articulated. It 
is the uppermost bone of the foot ; it has se- 
veral surfaces to be considered ; its upper, 
and somewhat posterior part, which is smooth 
and convex, is admitted into the cavity of the 
tibia. Its lateral parts are connected with the 
malleoli of the two bones of the leg ; below, 
it is articulated with the os calcis, and its an- 
terior surface is received by the os naviculare. 
All these articulations are secured by means 
of ligaments. 

R 



130 Osteology. 

The os calcis, or calcaneum, which is of a 
very irregular figure, is the largest bone of the 
foot. Behind, it is formed into a considerable 
tuberosity called the heel ; without this- tube- 
rosity, which supports us in an erect posture, 
and when we walk, we should be liable to fall 
backwards. 

On the internal surface of this bone, we 
observe a considerable sinuosity, which affords 
a passage to the tendon of a muscle : and to 
the posterior part of the os calcis, a strong 
tendinous cord called tendo achillis* is attach- 
ed, which is formed by the tendons of seve- 
ral muscles united together. The articulation 
of this with the other bones is secured by 
means of ligaments. 

The os naviculare, or scaphoides, (for these 
two terms have the same signification), is so 
called on account of its resemblance to a little 
bark. At its posterior part, which is concave, 
it receives the astragalus ; anteriorly it is ar- 
ticulated with the cuneiform bones, and late- 
rally is connected with the os cuboides. 

The os cuboides forms an irregular cube. 
Posteriorly it is articulated with the os calcis ; 
anteriorly it supports the two last bones of the 
metatarsus, and laterally it joins the third cu- 
neiform bone and the os naviculare. 
f Each of the ossa cuneiformia, which are 
three in number, resembles a wedge, and from 
this similitude their name is derived. They 

* This tendon is sometimes ruptured by jumping, dancing, 
or other violent efforts. 



Osteology. 131 

are placed next to the metatarsus by the sides 
of each other, and are usually distinguished 
into os cuneiforme externum, medium or mini- 
mum, and internum or maximum. The supe- 
rior surface of these bones, from their wedge- 
like shape, is broader than that which is be- 
low, where they help to form the sole of the 
foot ; posteriorly they are united to the os na- 
viculare, and anteriorly they support the three 
first metatarsal bones. 

When these seven bones composing the tar- 
sus are viewed together in the skeleton, they 
appear convex above, where they help to form 
the upper part of the foot ; and concave under- 
neath, where they form the hollow of the foot, 
in which the vessels, tendons, and nerves of 
the foot are placed secure from pressure. 

They are united to each other by very strong 
ligaments, and their articulation with the foot 
is secured by a capsular and two lateral liga- 
ments ; each of the latter is covered by an an- 
nular ligament of considerable breadth and 
thickness, which serves to bind down the ten- 
dons of the foot, and at the same time to 
strengthen the articulation. 

The os cuneiforme externum is joined late- 
rally to the os cuboides. 

These bones complete our account of the tar- 
sus. Though what we have said of this part 
of the osteology has been very simple and con- 
cise, yet many readers may not clearly under- 
stand it : but if they will be pleased to view 
these bones in their proper situation in the 



132 Osteology. 

skeleton, all that we have said of them will 
be easily understood. 

The metatarsus is made up of five bones, 
whereas the metacarpus consists only of four. 
The cause of this difference is, that in the 
hand the last bone of the thumb is not includ- 
ed among the metacarpal bones ; whereas in 
the foot the great toe has only two bones. The 
first of these bones supports the great toe and 
is much larger than the rest, which nearly re- 
semble each other in size. 

These bones are articulated by one extremi- 
ty with the cuneiform bones and the os cuboi- 
des, and by their other end with the toes. 

Each of the toes, like the fingers, consists of 
three bones, except the great toe, which is 
formed of two bones. Those of the other 
four are distinguished into three phalanges. 
Although the toes are more confined in their 
motion than the fingers, yet they appear to be 
perfectly fitted for the purposes they are de- 
signed for. In walking, the toes bring the 
centre of gravity perpendicular to the advanc- 
ed foot ; and as the soles of the feet are natu- 
rally concave, we can at pleasure increase this 
concavity, and form a kind of vault, which 
adjusts itself to the different inequalities that 
occur to us in walking; and which, without 
this mode of arrangement, would incommode 
us exceedingly, especially when bare-footed. 



Osteology. 133 



4. Of the Ossa Sesamoidea. 



Besides the bones we have already de- 
scribed, there are several small ones that are 
met with only in the adult skeleton, and in 
persons who are advanced in life ; which, from 
their supposed general resemblance to the 
seeds of the sesamum, are called ossa sesa- 
moidea. They are commonly to be seen at 
the first joint of the great toe, and sometimes 
at the joints of the thumb ; they are likewise 
now and then to be found at the lower extremity 
of the fibula, upon the condyles of the thigh- 
bone, under the os cuboides of the tarsus, and 
in other parts of the body. Their size and num- 
ber seem constantly to be increased by age and 
hard labour ; and as they are generally found 
in situations where tendons and ligaments are 
most exposed to the action of muscles, they 
are now generally considered as ossified por- 
tions of ligaments or tendons. 

The upper surface of these bones is usual- 
ly convex, and adherent to the tendon that co- 
vers it ; the side which is next to the joint is 
smooth and flat. Though their formation is 
accidental, yet they seem to be of some use, 
by raising the tendons farther from the centre 
of motion, and consequently increasing the 
power of the muscles. In the great toe and 
thumb they are likewise useful, by forming a 
groove for the flexor tendons. 



134 Osteology. 

EXPLANATION OF THE PLATES 
OF OSTEOLOGY. 

Plate. XIX. 

Fig. 1. A Front-view of the Male Skele- 
ton. 

A, The os frontis. B, The os parietale. C, 
The coronal suture. D, The squamous part 
of the temporal bones. E, The squamous su- 
ture. F, The zygoma. G, The mastoid pro- 
cess. H, The temporal process of the sphe- 
noid bone. I, The orbit. K, The os malae. 
L, The os maxillare superius. M, Its nasal 
process. N, The ossa nasi. O, The os un- 
guis. P, The maxilla inferior. Q, The teeth 
which are sixteen in number in each jaw. R, 
The seven cervical vertebrae, with their inter- 
mediate cartilages. S, Their transverse pro- 
cesses. T, The twelve dorsal vertebrae, with 
their intermediate cartilages. U, The five 
lumbar vertebrae. V, Their transverse pro- 
cesses. W, The upper part of the os sacrum. 
X, Its lateral parts. The holes seen on its 
fore part are the passages of the undermost 
spinal nerves and small vessels. Opposite to 
the holes, the marks of the original divisions 
of the bone are seen. Y, The os ilium. Z, 
Its crest or spine, a, The anterior spinous 
processes, b, The brim of the pelvis, c 



Osteology. 135 

The ischiatic niche, d, The os ischium, e, 
Its tuberosity, f, Its spinous process- g, Its 
crus. h, The foramen thyroideum. i, The 
os pubis, k, The symphysis pubis. 1, The 
crus pubis, m, The acetabulum, n, The se- 
venth or last true rib- o, The twelfth or last 
false rib. p, The upper end of the sternum, 
q, The middle piece, r, The under end, or 
cartilage ensiformis. s, The clavicle, t, The 
internal surface of the scapula, u, Its acro- 
mion, v, Its coracoid process- w, Its cervix. 
x, The glenoid cavity, y, The os humeri, z, 
Its head which is connected to the glenoid ca- 
vity. 1, Its external tubercle. 2, Its r inter- 
nal tubercle. 3. The groove for lodging the 
long head of the biceps muscle of the arm. 
4, The internal condyle. 5, The external 
condyle. Between 4 and 5, the trochlea. 6, 
The radius. 7, Its head- 8, Its tubercle. 9, 
The ulna- 10, Its coronoid process. 11, 12, 
13, 14, 15, 16, 1^, 18, The carpus; compos- 
ed of os naviculare, os lunare, os cuneifor- 
me, os pisiforme, os trapezium, os trapezoi- 
des, os magnum, os unciforme. 19, The five 
bones of the metacarpus. 20, The two bones 
of the thumb. 21, The three bones of each 
of the fingers. 22, The os femoris. 23, Its 
head. 24, Its cervix. 25, The trochanter 
major. 26, The trochanter minor. 27, The 
internal condyle. 28, The external condyle 
29, The rotula. 30, The tibia. 31, Its head- 
32, Its tubercle. 33, Its spine. 34, The mal- 
leolus internus. 35, The fibula. 36, Its head. 
37 y The malleolus externus. The tarsus i§ 



136 Osteology. 

composed of, 38, The astragalus; 39, The 
os calcis ; 40, The os naviculare ; 41, Three 
ossa cuneiformia, and the os cuboides, which 
is not seen in this figure. 4^, The five bones 
of the metatarsus. 43, The two bones of 
the great toe. 44, The three bones of each 
of the small toes. 

Fig. 2. A Front-view of the Skull. 

A, The os frontis. B. The lateral part 
of the os frontis, which gives origin to part of 
the temporal muscle. C, The superciliary- 
ridge. D, The superciliary hole through 
which the frontal vessels and nerves pass. E 
E, The orbitar processes. F, The middle of 
the transverse suture. G, The upper part of 
the orbit. H, The foramen opticum. I, The 
foramen lacerum. K, The inferior orbitar fis- 
sure. L, The os unguis. M, The ossa na- 
si. N, The os maxillare superius. O, Its na- 
sal process. P, The external orbitar hole 
through which the superior maxillary vessels 
and nerves pass. Q, The os malae. R, A 
passage for small vessels into, or out of, the 
orbit. S, The under part of the left nostril. 
T, The septum narium. U, The os spongi- 
osum superius. V, The os spongiosum infe- 
rius. W, The edge of the alveoli, or spongy 
sockets, for the teeth- X, The maxilla infe- 
rior. Y, The passage for the inferior maxil- 
lary vessels and nerves. 



Osteology. 137 



Fig. 3. A Side-view of the Skull, 

A, The os frontis, B, The coronal suture. 
C, The os parietale. D, An arched ridge 
which gives origin to the temporal muscle. E, 
The squamous suture, F, The squamous 
part of the temporal bone ; and, farther for- 
wards, the temporal process of the sphenoid 
bone. G, The zygomatic process of the tem- 
poral bone. H, The zygomatic suture. I, The 
mastoid process of the temporal bone. K, The 
meatus auditorius externus. L, The orbitar 
plate of the frontal bone, under which is seen 
the transverse suture. M, The pars plana of 
the ethmoid bone. N, The os unguis. O, 
The right os nasi. P, The superior maxilla- 
ry bone. Q, Its nasal process. R, The two 
dentes incisores. S, The dens caninus. T, 
The two small molares. U, The three large 
molares- V, The os malas. W, The lower 
jaw. X, Its angle. Y, The coronoid process. 
Z, The condyloid process, by which the jaw 
is articulated with the temporal bone. 

Fig. 4. The posterior and right Side of the 

Skull. 

A, The os frontis. B B, The ossa parieta- 
lia. C, The sagittal suture, D, The parie- 
tal hole, through which a small vein runs to 
the superior longitudinal sinus. E, The lamb- 
doid suture. F F, Ossa triquetra. G, The 
os occipitis. H, The squamous part of the 
temporal bone. I, The mastoid process. K, 

S 



138 Osteology. 

The zygoma. L, The os malae. M, The tem- 
poral part of the sphenoid bone. N, The su- 
perior maxillary bone and teeth. 

Fig. 5. The external Surface of the Os Fron- 

tis. 

A, The convex part. B, Part of the tem- 
poral fossa. C, The external angular process. 
D, The internal angular process. E, 1 he na- 
sal process. F, The superciliary arch. G, 
The superciliary hole. H, The orbitar plate. 

Fig. 6. The Interior Surface of the Os Fron- 

tis. 

A A, The serrated edge which assists to 
form the coronal suture. B, The external an- 
gular process. C, The internal angular pro- 
cess. D, The nasal process. E, 1 he orbi- 
tar plate. F, The cells which correspond with 
those of the ethmoid bone. G, The passage 
from the frontal sinus. H, The opening which 
receives the cribriform plate of the ethmoid 
bone. I, The cavity which lodges the fore 
part of the brain. K, The spine to which the 
falx is fixed. L, The groove which lodges 
the superior longitudinal sinus. 

PLATE XX. 

Fig. 1. A Back-view of the Skeleton. 

A A, The ossa parietalia. B, The sagit- 
tal suture. C, The lambdoid suture. D, 1 he 



Osteology. 139 

occipital bone. E, The squamous suture. F, 
The mastoid process of the temporal bone. 
G, The os malae. H, The palate-plates of the 
superior maxillary bones. I, Ine maxilla in- 
ferior. K, The teeth of both jaws. L, The 
seven cervical vertebras. M, Their spinous 
processes. N, Their transverse and oblique 
processes. O, The last of the twelve dorsal 
vertebrae. P, The fifth or last lumbar vertebra. 
Q, The transverse processes. R, The obli- 
que processes. S, The spinous processes. T, 
The upper part of the os sacrum. U, The 
posterior holes which transmit small blood- 
vessels and nerves. V, The under part of 
the os sacrum which is covered by a mem- 
brane. W, The os coccygis. X, The os ili- 
um. Y, Its spine or crest. Z, The ischia- 
tic niche, a, The os ischium, b, Its tubero- 
sity, c, Its spine, d, The os pubis, e, The 
foramen hydroideum. f, The seventh or last 
true rib. g, The twelfth or last false rib. h, 
The clavicle, i, The scapula, k, Its spine. 
1, Its acromion, m, Its cervix, n, Its supe- 
rior costa. o, Its posterior costa. p, Its infe- 
rior costa. q, The os humeri, r, The radi- 
us. Sj The ulna, t, Its oleclarnon. u, All 
the bones of the carpus, excepting the os pi- 
siforme, which is seen in plate XIX- fig. 1. 
v, The five bones of the metacarpus, w, The 
two bones of the thumb, x, The three bones 
of each of the fingers, y, The two sesamoid 
bones at the root of the left thumb, z, The 
os femoris. 1, The trochanter major. 2, The 



140 Osteology. 

trochanter minor. 3, The linea aspera. 4, The 
internal condyle. 5, The external condyle. 6 6, 
The semilunar cartilages. 7, The tibia. 8, The 
malleolus internus. 9, The fibula. 10, The 
malleolus externus. 11, The tarsus. 12, The 
metatarsus. 13, The toes- 

Fig- 2« The External Surface of the left Os 
Parietale. 

A, The convex smooth surface- B, The pari- 
etal hole. C, An arch made by the beginning 
of the temporal muscle. 

Fie 3. The Internal Surface of the same bone. 

A, Its superior edge, which, joined with 
the other, forms the sagittal suture- B, The 
anterior edge, which assists in the formation 
of the coronal suture. C. The inferior edge 
for the squamous suture. D, The posterior 
edge for the lambdoid suture. E, A depres- 
sion made by the lateral sinus- F F, The 
prints of the arteries of the dura mater. 

Fig. 4. The External Surface of the Left Os 
Temporum- 

A, The squamous part- B, The mastoid pro- 
cess. C, The zygomatic process. D, The 
styloid process. E, The petrosal process. F. 
The meatus auditorius externus. G, The gle- 
noid cavity for the articulation of the lower 
jaw. H, The foramen stylo-mastoideum for 
the portio dura of the seventh pair of nerves 
I, Passages for blood-vessels into the bone. 



Osteology. 141 

K, The foramen mastoideum through which 
a vein goes to the lateral sinus- 

Fig. 5- The Internal Surface of the Left Os 
Temporum. 

A, The squamous part; the upper edge of 
which assists in forming the squamous suture. 
B, The mastoid process. C, The styloid pro- 
cess. D, The pars petrosa. E, The entry of 
the seventh pair, or auditory nerve. F, The 
fossa which lodges a part of the lateral sinus. 
G, The foramen mastoideum. 

Fig- 6. The External Surface of the Osse- 
ous Circle, which terminates the meatus 
auditorius externus. 

A, The anterior part. B, A small part of 
the groove in which the membrana tympani 
is fixed. 

N- B. This with the subsequent bones of 
the ear, are here delineated as large as the life. 

Fig. 7. The Internal Surface of the Osseous 
Circle- 

A, The anterior part- B, The groove in 
which the membrana tympani is fixed- 

Fig- 8. The Situation and Connection of the 
Small Bones of the Ear. 

A, The malleus. B, The incus- C, The os 
orbiculare. D, The stapes- 



142 Osteology. 

Fig. 9. The Malleus, with its Head, Handle, 
and Small processes. 

Fig. 10» The Incus, with its Body, Superior 
and Inferior Branches. 

Fig. 11. The Os Orbiculare. 

Fig. 12. The Stapes, with its Head, Base, 
and two Crura. 

Fig- 13. An Internal View of the Labyrinth 
of the Ear. 

A, The hollow part of the cochlea, which 
forms a share of the meatus auditorius inter- 
nus- B, The vestibulum. C C C, The semi- 
circular canals. 

Fig- 14. An External View of the Labyrinth. 

A, The semicircular canals. B, The fenes- 
tra ovalis which leads into the vestibulum. C, 
The fenestra rotunda which opens into the 
cochlea. D, The different turns of the cochlea. 

Fig. 15« The Internal Surface of the Os Sphe- 

NOIDES. 

A A, The temporal processes- B B, The 
pterygoid processes. C C, The spinous pro- 
cesses. D D, The anterior clinoid processes. 
E, The posterior clinoid process- F, The an- 
terior process which joins the ethmoid bone. 
G, The sella turcica for lodging the glandula 
pituitaria. H, The foramen opticum. K, The 
foramen lacerum. L, The foramen rotun- 



Osteology. 143 

dum. M, The foramen ovale. N, The fora- 
men spinale. 

Fig. 16. The External Surface of the Os 
Sphenoides. 

A A, The temporal processes. B B, The 
pterygoid processes. C C, The spinous pro- 
cesses. D, The processus azygos. E, The 
small triangular processes which grow from 
the body of the bone. F F, The orifices of 
the sphenoidal sinuses. G, The foramen la- 
cerum. H, The foramen rotundum. I, The 
foramen ovale. K, The foramen pterygoide- 
um. 

Fig. 17. The External View of the Os Eth- 

MOIDES. 

A, The nasal lamella. B B, The grooves 
between the nasal lamella and ossa spongiosa 
superiora. C C, The ossa spongiosa superio- 
ra. D D, The sphenoidal cornua. See Fig. 
16. E. 

Fig. 18- The Internal View of the Os Eth- 
moides. 

A, The crista galli- B, The cribriform 
plate, with the different passages of the ol- 
factory nerves. C C, Some of the ethmoidal 
cells. D, The right os planum. E E, The 
sphenoidal cornua- 

Fig. 19- The right Sphenoidal Cornu. 

Fig. 20. The left Sphenoidal Cornu. 



144 Osteology. 

Fig. 21. The External Surface of the Os Oc- 

CIPITIS. 

A, The upper part of the bone. B, The 
superior arched ridge- C, The inferior arch- 
ed ridge. Under the arches are prints made 
by the muscles of the neck. D D, The two 
condyloid processes which articulate the head 
with the spine. E, The cuneiform process. 
F, The foramen magnum through which the 
spinal marrow passes. G G, The posterior 
condyloid foramina which transmit veins into 
the lateral sinuses. H H, The foramina lin- 
gualia for the passage of the nine pair of 
nerves. 

Fig. 22. The Internal Surface of the Os Oc- 

CIPITIS. 

A A, The two sides which assist to form 
the lambdoid suture. B, The point of the 
cuneiform process, where it joins the sphe- 
noid bone. C C, The prints made by the 
posterior lobes of the brain- D D, Prints 
made by the lobes of the cerebellum. E, The 
cruciform ridge for the attachment of the pro- 
cesses of the dura mater. F, The course of 
the superior longitudinal sinuses- G G, The 
course of the two lateral sinuses. H, The 
foramen magnum. II, The posterior condy- 
loid foramina. 



Osteology. 145 

Plate XXI. 

Fig. 1' A Side-view of the Skeleton, 

A A, The ossa parietalia. B, The sagittal 
suture. C, The os occipitis. D D, The lamb- 
doid suture. E, The squamous part of the tem- 
poral bone. F, The mastoid process. G, The 
meatus auditorius externus. H, The os fron- 
tis. I, The os mala?. K, The os maxillare 
superius. L, The maxilla inferior. M, The 
teeth of both jaws. N, The seventh, or last 
cervical vertebra- O, The spinous processes. 
P, Their transverse and oblique processes. Q, 
The twelfth or last dorsal vertebra. R, The 
fifth, or last lumbar vertebra. S. The spinous 
processes. T, Openings between the verte- 
brae for the passage of the spinal nerves. U, 
The under end of the os sacrum. V, The 
os coccygis. W, The os ilium. X, The an- 
terior spinous processes. Y, The posterior 
spinous processes. Z, The ischiatic niche- a, 
The right os ilium. b, The ossa pubis, c, 
The tuberosity of the left os ischium, d, The 
scapula, e, Its spine, f, The os humeri, g, 
The radius, h, The ulna, i, The carpus, k, 
The metacarpal bone of the thumb. 1, The 
metacarpal bones of the fingers, m, The two 
bones of the thumb, n, The three bones of 
each of the fingers, o, The os femoris. p, 
Its head- q, The trochanter major, r, The 
external condyle- s, The rotula. t, The tibia. 

T 



146 Osteology. 

u, The fibula, v, The malleolus externus. 
w, The astragalus, x, The os calcis. y, The 
os naviculare. z, The three ossa cuneiibrmia. 
1, The os cuboides. 2, The five metatarsal 
bones. 3, The two bones of the great toe. 4, 
The three bones of each of the small toes. 

Fig. 2- A View of the Internal Surface of the 
Base of the Skull. 

AAA, The two tables of the skull with 
the diploe. B B, The orbitar plates of the 
frontal bone. C, i he crista galli, with cribri- 
form plate of the ethmoidal bone on each side 
of it, through which the first pair of nerves 
pass. D, The cuneiform process of the occipi- 
tal bone. E, The cruciform ridge. F, The 
foramen magnum for the passage of the spi- 
nal marrow. G, The zygoma, made by the 
joining of the zygomatic processes of the os 
temporum and os malas. H, The pars squa- 
mosa of the os temporum. I, The pars mam- 
millaris. K, The pars petrosa. L, The tem- 
poral process of the sphenoid bone. M M, 
The anterior clinoid processes. N, The pos. 
terior clinoid process. O, The sella turcica. 
P, The foramen opticum, for the passage of 
the optic nerve and ocular artery of the left 
side. Q, The foramen lacerum, for the third, 
fourth, sixth, and first of the fifth pair of nerves 
and ocular vein. R, The foramen rotundum, 
for the second of the fifth pair. S, The fora- 
men ovale, for the third of the fifth pair. T, 
The foramen spinale, for the principal artery 
of the dura mater. U, The entry of the au- 



„ v/ 




Osteology. 147 

ditory nerve- V, The passage for the lateral 
sinus. W, The passage of the eighth pair of 
nerves. X, The passage of the ninth pair- 

Tig. 3- A View of the External Surface of the 
Base of the Skull. 

A, The two dentes incisores of the right 
side. B, The dens caninus- C, The two small 
molares. D, The three large molares. E, The 
foramen incisivum, which gives passage to 
small blood-vessels and nerves. F, The palate- 
plates of the ossa maxillaria and palati, joined 
by the longitudinal and transverse palate su- 
tures. G, The foramen palatinum posteritts, 
for the palatine vessels and nerves- H, 'I he 
os maxillare superius of the right side. 1, The 
os malse. K, The zygomatic process of the 
temporal bone. L, 1 he posterior extremity of 
the ossa spongiosa. M, The posterior extre- 
mity of the vomer, which forms the back- part 
of the septum nasi. N, The pterygoid proeess 
of the right side of the sphenoid bone. O O, The 
foramina ovalia. PP, The foramina spinal ia. 
Q Q,, The passages of the internal carotid ar- 
teries. R, A hole between the point of each pars 
petrosa and cuneiform process of the occipital 
bone, which is filled up with a ligamentous sub- 
stance in the recent subject- S, The passage 
of the left lateral sinus. T, The posterior 
condyloid foramen of the left side. U, The 
foramen mastoideum. V, The foramen mag- 
num. W, The inferior orbitar fissure. X, The 
glenoid cavity, for the articulation of the low- 
er jaw. Y, The squamous part of the temporal 



148 Osteology. 

bone. Z, The mastoid process, at the inner 
side of which is a fossa for the posterior belly 
of the digastric muscle, a, 1 he styloid pro- 
cess, b, i he meatus auditorius externus. c, 
1 he left condyle of the occipital bone, d, The 
perpendicular occipital spine, e e, The infe- 
rior horizontal ridge of the occipital bone, ff, 
The superior horizontal ridge, which is oppo- 
site to the crucial ridge where the longitudinal 
sinus divides to form the lateral sinuses. ^%g^ 
The lam'odoid suture, h, The left squamous su- 
ture, i, The parietal bone- 

Fjg. 4. The anterior surface of the Ossa 

Nasi. 

A, The upper part, which joins the os fron- 
tis. B, The under end, which joins the car- 
tilage of the nose. C, The inner edge, where 
they join each other. 

Fig. 5. The posterior surface of the Ossa 

Nasi. 

A A, Their cavity, which forms part of the 
arch of the nose. B B, Their ridge or spine, 
which projects a little to be fixed to the fore- 
part of the septum narium. 

Fig. 6. The external surface of the Os Max- 
illare Superius of the left side.. 

A, The nasal process. B, The orbitar 
plate. C, The unequal surface which joins 
the os mabs. D, The external orbitar hole. 
E, The opening into the nostril. F, The pa- 



Osteology, 149 

late-plate. G, The maxillary tuberosity. H, 
Part of the os palati. I, The two dentes inci- 
sores. K, The dens caninus. L, The two 
small dentes molares. M, The three large 
dentes molares. 

Fig. 7. The internal surface of the Os Max- 
illare Superius and Os Palati. 

A, The nasal process. B B, Eminences for 
the connection of the os spongiosum inferius. 

D, The under end of the lachrymal groove. 

E, The antrum maxillare. F, The nasal spine, 
between which and B is the cavity of the nos- 
tril. G, The palate-plate. H, The orbitar 
part of the os palati. I, The nasal plate. K, 
The suture which unites the maxillary and pa- 
late bones. L, The pterygoid process of the 
palate bones. 

Fig. 8. The external surface of the right Os 

Unguis. 

A, The orbitar part. B, The lachrymal part. 
C, The ridge between them. 

Fig. 9. The internal surface of the right Os 

Unguis. 

This side of the bone has a furrow opposite 
to the external ridge ; all behind that is irre- 
gular, where it covers part of the ethmoidal 
cells. 



150 Osteology. 

Fig. 10. The external surface of the left Os 

MaLJE. 

A, The superior orbitar process. B, The 
inferior orbitar process. C, The malar pro- 
cess. D, Ihe zygomatic process. E, The 
orbitar plate. F, A passage for small vessels 
into or out of the orbit. 

Fig. 11. The internal surface of the left Os 

Male. 

A, The superior orbitar process. B, The 
inferior orbitar process. C, The malar pro- 
cess. D, The zygomatic process. E, The 
internal orbitar plate or process. 

Fig. 12. The external surface of the right Os 
Spongiosum Inferius. 

A, The anterior part. B, The hook-like 
process for covering part of the antrum maxil- 
lare. C, A small process which covers part 
of the under end of the lachrymal groove. 
D, The inferior edge turned a little outwards. 

Fig. 13. The internal surface of the Os Spon- 
giosum Inferius. 

A, The anterior extremity. B, The upper 
edge which joins the superior maxillary and 
palate bones. 

Fig. 14. The posterior and external surface 
of the right Os Pal at i. 

A, The orbitar process. B, The nasal la- 
mella. C, The pterygoid process. D, The 
palate process. 



Osteology. 151 

Fig. 15. The anterior and external surface 
of the right Os Palati. 

A, The orbitar process. B, An opening 
through which the lateral nasal vessels and 
nerves pass. C, The nasal lamella. D, The 
pterygoid process- E, The posterior edge of 
the palate process for the connection of the 
velum palati. F, The inner edge by which 
the two ossa palati are connected. 

Fig. 16- The right side of the Vomer, 

A, The upper edge which joins the nasal 
lamella of the ethmoid bone and the middle 
cartilage of the nose. B, The inferior edge, 
which is connected to the superior maxillary 
and palate bones. C, The superior and pos- 
terior part which receives the processus azy- 
gos of the sphenoid bone. 

Fig. 17- The Maxilla Inferior. 

A, The chin- B, The base and left side. 
C, The angle. D, The coronoid process. E> 
The condyloid process. F, The beginning of 
the inferior maxillary canal of the right side, 
for the entry of the nerve and blood-vessels. 
G, The termination of the left canal. H, The 
two dentes incisores. I, The dens caninus. K, 
The two small molares. L, The three large 
molares. 

Fig. 18. The different classes of the Teeth. 

1, 2, Afore and back view of the two ante- 
rior dentes incisores of the lower jaw. 3, I. 



152 Osteology. 

Similar teeth of the upper jaw. 5, 6, A ibre 
and back view of the dentes canini. 7, 8, 
The anterior dentes molares. 9, 10, 11, The 
posterior dentes molares. 12, 13, 14, 15, 16, 
Unusual appearances in the shape and size of 
the teeth. 

Fig. 19. The external surface of the Os Hy 

oides. 

A, The body. B B, The cornua. C C, 
The appendices. 



Plate XXII. 

Fig. 1. A Posterior View of the Sternum 
and Clavicles, with the ligament connect- 
ing the clavicles to each other. 

a, The posterior surface of the sternum, 
b b, The broken ends of the clavicles, c c c c, 
The tubercles near the extremity of each cla- 
vicle, d, The ligament connecting the cla- 
vicles. 

Fig. 2. A Fore-view of the Left Scapula, 
and of a half of the Clavicle, with their 
Ligaments. 

a, The spine of the scapula, b, the acro- 
mion, c, The inferior angle- d, Inferior cos- 
ta. e, Cervix, f, Glenoid cavity, covered 
with cartilage for the arm-bone, g g, The 
capsular ligament of the joint- h, CoracouJ 



Osteology. 153 

process, i, The broken end of the clavicle. 
k, Its extremity joined to the acromion. 1, A 
ligament coming out single from the acromion 
to the coracoid process, m, A ligament com- 
ing out single from the acromion, and dividing 
into two, which are fixed to the coracoid pro- 
cess. 

Fig. 3. The Joint of the Elbow of the Left 
Arm, with the Ligaments. 

a, The os humeri, b, Its internal condyle. 
c c, The two prominent parts of its trochlea 
appearing through the capsular ligament, d, 
The ulna, e, The radius, f, The part of the 
ligament including the head of the radius. 

Fig. 4. The Bones of the Right-Hand, with 
the Palm in view. 

a, The radius, b, The ulna, c, The sca- 
phoid bone of the carpus, d, The os lunare. 
e, The os cuneiforme. f, The os pisiforme. 
g, Trapezium, h, Trapezoides. i, Capita- 
turn, k, Unciforme. 1, The four metacar- 
pal bones of the fingers, m, The first pha- 
lanx, n, The second phalanx, o, The third 
phalanx, p, The metacarpal bone of the 
thumb, q, The first joint, r, The second 
joint. 

Fig. 5. The Posterior View of the Bones of 
the Left Hand- 

The explication of Fig. 4. serves for this 
figure ; the same letters pointing out the same 
bones, though in a different view. 

U 



154 Osteology, 

Fig. 6. The Upper Extremity of the Tibia, 
with the Semilunar Cartilages of the Joint 
of the Knee, and some Ligaments. 

a, The strong ligament which connects 
the rotula to the tubercle of the tibia, b b, 
The parts of the extremity of the tibia, co- 
vered with cartilage, which appear within the 
semilunar cartilages, c c, The semilunar car- 
tilages- d, The two parts of what is called 
the cross ligament. 

Fig. 7- The Posterior View of the Joint of 
the Right Knee. 

a, The os femoris cut- b, Its internal con- 
dyle, c, Its external condyle, d, The back 
part of the tibia, e, The superior extremity 
of the fibula, f, The edge of the internal se- 
milunar cartilage, g, An oblique ligament, 
h, A larger perpendicular ligament, i, A li- 
gament connecting the femur and fibula. 

Fig. 8- The Anterior View of the Joint of 
the Right Knee. 

b, The internal condyle- c, Its external 
condyle, d, The part of the os femoris, on 
which the patella moves- e, A perpendicu- 
lar ligament, f f, The two parts of the cru- 
cial ligaments, g g, The edges of the two 
moveable semilunar cartilages, h, The tibia, 
i, The strong ligament of the patella, k, The 
back part of it where the fat has been dis- 
sected away. 1, The external depression, m, 
The internal one. n, The cut tibia. 



Osteology. 155 

Fig. 9. A View of the inferior part of the 
Bones of the Right Foot. 

i a, The great knob of the os calcis. b, A 
prominence on its outside- c, The hollow 
for the tendons, nerves, and blood-vessels, d, 
The anterior extremity of the os calcis. e, 
Part of the astragalus, f, Its head covered 
with cartilage, g, The internal prominence 
of the os naviculare. h, The os cuboides. 
i, The os cuneiforme internum ; k, — Medium ; 
1, — Externum, m, The metatarsal bones of 
the four lesser toes, n, The first — o, The 
second — p, The third phalanx of the four les- 
ser toes, q, The metatarsal bones of the great 
toe. r, Its first — s, Its second joint. 

Fig. 10- The Inferior Surface of the two large 
Sesamoid Bones, at the first Joint of the 
Great Toe. 

Fig. 11. The Superior View of the Bones of 
the Right Foot. 

a, b, as in Fig- 9. c, The superior head of 
the astragalus, d, &c . as in Fig. 9. 

Fig. 12. The View of the Sole of the Foot, 
with its Ligaments. 

a, The great knob of the os calcis. b, The 
hollow for the tendons, nerves, and blood- 
vessels, c, The sheaths of the flexores pol- 
licis and digitorum longi opened, d, The 
strong cartilaginous ligament supporting the 
head of the astragalus, e, h, Two ligaments 
which unite into one, and are fixed to the 



156 Osteology. 

metatarsal bone of the great toe. f, A liga- 
ment from the knob of the os calcis to the 
metatarsal bone of the little toe. g, A strong 
triangular ligament, which supports the bones 
of the tarsus, i, The ligaments of the joints 
of the five metatarsal bones. 

Fig. 13. a, The head of the thigh bone of 
a child, b, The ligamentum rotundum con- 
necting it to the acetabulum, c, The capsu- 
lar ligament of the joint with its arteries in- 
jected, d, The numerous vessels of the mu- 
cilaginous gland injected. 

Fig. 14. The Back-view of the Cartilages of 
the Larynx, with the Os Hyoides. 

a, The posterior part of the base of the os 
hyoides. b b, Its cornua. c, The appendix 
of the right side, d, A ligament sent out 
from the appendix of the left side, to the sty- 
loid process of the temporal bone, e, The 
union of the base with the left cornu. f f, 
The posterior sides of (g) the thyroid carti- 
lage, h h, Its superior cornua. i i, Its in- 
ferior cornua. k, The cricoid cartilage. 1 1, 
The arytenoid cartilages, m, The entry into 
the lungs, named glottis, n, The epiglottis, 
o o, The superior cartilages of the trachea. 
p, Its ligamentous back part. 

Fig. 15. The Superior Concave surface of the 
Sesamoid Bones at the first joint of the 
Great Toe, with their Ligaments. 

a, Three sesamoid bones. b, The liga- 
mentous substance in which they are formed. 



Of the Integuments, &c. 157 



Part II. OF THE SOFT PARTS IN GE- 
NERAL ; 

Of the Common Integuments, with their appen- 
dages ; and of the Muscles. 

ANATOMICAL writers usually proceed 
to a description of the muscles after 
having finished tne osteology ; but we shall 
deviate a little from the common method, with 
a view to describe every thing clearly and dis- 
tinctly, and to avoid a tautology which would 
otherwise be unavoidable. All the parts ot 
the body are so intimately connected with each 
other, that it seems impossible to convey a just 
idea of any one of them, without being in some 
measure obliged to say' something of others ; 
and on this account we wish to mention in this 
place the names and situation of the principal 
viscera of the body, that when mention is 
hereafter made of any one of them in the 
course of the work, the reader may at least 
know where they are placed. 

After this little digression, the common in- 
teguments, and after them the muscles will be 
described ; we then propose to enter into an 
examination of the several viscera and their 
different functions. In describing the brain. 



158 Of the Integuments, &c. 

occasion will be taken to speak of the nerves 
and animal spirits. The circulation of the 
blood will follow the anatomy of the heart, and 
the secretions and other matters will be intro- 
duced in their proper places. 

The body is divided into three great cavities. 
Of these the uppermost is formed by the bones 
of the cranium, and incloses the brain and cere- 
bellum. 

The second is composed of the vertebrae of 
the back, the sternum, and true ribs, with the 
additional assistance of muscles, membranes, 
and common integuments, and is called the 
thorax — It contains the heart and lungs. 

The third, and inferior cavity, is the abdo- 
men. It is separated from the thorax by 
means of the diaphragm, and is formed by 
the lumbar vertebrae, the os sacrum, the os- 
sa innominata, and the false ribs, to which we 
may add the peritonaeum, and a variety of 
muscles. This cavity incloses the stomach, 
intestines, omentum or cawl, liver, pancreas, 
spleen, kidneys, urinary bladder, and parts of 
generation. 

Under the division of common integuments 
are usually included the epidermis, or scarf- 
skin, the reticulum mucosum of Malpighi, 
the cutis or true skin, and the membrana adi- 
posa — The hair and nails, as well as the se- 
baceous glands, may be considered as appen- 
dages to the skin. 






Of the Integuments, &c. 159 



Sect. I. Of the Skin. 



1. Of the ScAKT-skin. 

The epidermis, cuticula, or scarf-skin, is 
a fine, transparent, and insensible pellicle, des- 
titute of nerves and blood-vessels, which in- 
vests the body, and every where covers the 
true skin. This scarf-skin, which seems to 
be very simple, appears, when examined with 
a microscope, to be composed of several la- 
minae or scales which are increased by pres- 
sure, as we may observe in the hands and 
feet, where it is frequently much thickened, 
and becomes perfectly callous. It seems to 
adhere to the cutis by a number of very mi- 
nute filaments, but may easily be separated 
from it by heat, or by maceration in water- 
Some anatomical writers have supposed that it 
is formed by a moisture exhaled from the whole 
surface of the body, which gradually hardens 
when it comes into contact with the air. They 
were perhaps induced to adopt this opinion, 
by observing the speedy regeneration of this 
part of the body when it has been by any means 
destroyed, it appearing to be renewed on all 
parts of the surface at the same time ; where- 
as other parts which have been injured, are 
found to direct their growth from their circum- 
ference only towards their centre. But a demon- 
strative proof that the epidermis is not a fluid 



160 Of the Integuments, &c. 

hardened by means of the external air, is that 
the foetus in utero is found to have this cover- 
ing. Lieuwenhoeck supposed its formation to 
be owing to the expansion of the extremities 
of the excretory vessels which are found eve- 
ry where upon the surface of the true skin. 
Ruysch attributed its origin to the nervous 
papillae of the skin; and Heister thinks it pro- 
bable, that it may be owing both to the pa- 
pillae and the excretory vessels. The cele- 
brated Morgagni, on the other hand, contends,* 
that it is nothing more than the surface of the 
cutis, hardened and rendered insensible by the 
liquor amnii in utero, and by the pressure of 
the air. This is a subject, however, on which 
we can advance nothing with certainty. 

The cuticle is pierced with an infinite num- 
ber of pores or little holes, which afford a 
passage to the hairs, sweat, and insensible per- 
spiration, and likewise to warm water, mer- 
cury, and whatever else is capable of being 
taken in by the absorbents of the skin. The 
lines which we observe on the epidermis be- 
long to the true skin. The cuticle adjusts it- 
self to them, but does not form them. 

2. Of the Rete Mucosum. 

Between the epidermis and cutis we meet 
with an appearance to which Malpighi, who 
first described it, gave the name of rete muco- 
sum, supposing it to be of a membranous 
structure, and pierced with an infinite number 
of pores; but the fact is, that it seems to be 

* Adversar. Anat. 1 1. Animadvcr. 2. 



Of the Integuments, £sfc. 161 

nothing more than a mucous substance which 
may be dissolved by macerating it in water, 
while the cuticle and cutis preserve their tex- 
ture. 

The colour of the body is found to depend 
on the colour of this rete mucosum; for in ne- 
groes it is observed to be perfectly black, whilst 
the true skin is of the ordinary colour. 

The blisters which raise the skin when burnt 
or scalded, have been supposed by some to be 
owing to a rarefaction of this mucus ; but they 
are more probably occasioned by an increased 
action of the vessels of the part, together with 
an afflux and effusion of the thinner parts of 
the blood- 

3. Of the Cutis, or True Skin. 

The cutis is composed of fibres closely 
compacted together, as we may observe in lea- 
ther, which is the prepared skin of animals. 
These fibres form a thick net-work, which 
every where admits the filaments of nerves, 
and an infinite number of blood-vessels and 
lymphatics. 

The cutis, when the epidermis is taken off, 
is found to have, throughout its whole sur- 
face, innumerable papillae, which appear like 
very minute granulations, and seem to be cal- 
culated to receive the impressions of the touch, 
being the most easily observed where the sense 
of feeling is the most delicate, as in the palms 
of the hands and on the fingers, 

X 



162 Of the Integuments, &c. 

These papillae are supposed by many ana- 
tomical writers to be continuations of the pul- 
py substance of nerves, whose coats have ter- 
minated in the cellular texture of the skin. 
The great sensibility of these papillae evi- 
dently proves them to be exceedingly nervous; 
but surely the nervous fibrellac of the skin are 
of themselves scarcely equal to the formation 
of these papillse, and it seems to be more pro- 
bable that they are formed like the rest of the 
cutis. 

These papilla? being described, the uses of 
the epidermis and the reticulum mucosum will 
be more easily understood ; the latter serving 
to keep them constantly moist, while the for- 
mer protects them from the external air, and 
modifies their too great sensibility. 

4. Of the Glands of the Skin. 

In different parts of the body we meet, 
within the substance of the skin, with certain 
glands or follicles, which discharge a fat and 
oily humour that serves to lubricate and soft- 
en the skin. When the fluid they secrete 
has acquired a certain degree of thickness, it 
approaches to the colour and consistence of 
suet ; and from this appearance they have de- 
rived their name of sebaceous glands. They 
are found in the greatest number in the nose, 
ear, nipple, axilla, groin, scrotum, vagina, 
and prepuce. 

Besides these sebaceous glands, we read, 
in anatomical books, of others that are de- 



Of the Integuments, &c. 163 

scribed as small spherical bodies placed in all 
parts of the skin, in much greater abundance 
than those just now mentioned, and named mi- 
liary, from their supposed resemblance to mil- 
let-seed. Steno, who first described these 
glands, and Malpighi, Ruysch, Verheyen, 
Windslow, and others, who have adopted his 
opinions on this subject, speak of them as hav- 
ing excretory ducts, that open on the surface 
of the cuticle, and distil the sweat and mat- 
ter of insensible perspiration ; and yet, not- 
withstanding the positive manner in which these 
pretended glands have been spoken of, we are 
now sufficiently convinced that their existence 
is altogether imaginary. 

5. Of the Insensible Perspiration and Sweat. 

The matter of insensible perspiration, or in 
other words, the subtile vapour that is continu- 
ally exhaling from the surface of the body, is 
not secreted by any particular glands, but 
seems to be derived wholly from the extremities 
of the minute arteries that are everywhere dis- 
persed through the skin. These exhaling ves- 
sels are easily demonstrated in the dead sub- 
ject, by throwing water into the arteries ; for 
then small drops exude from all parts of the 
skin, and raise up the cuticle, the pores of which 
are closed by death ; and in the living subject, 
a looking-glass placed against the skin, is soon 
obscured by the vapour. Bidloo fancied he 
had discovered ducts leading from the cutis to 



164 Of the Integuments, &c. 

the cuticle, and transmitting this fluid ; but in 
this he was mistaken. 

Wiien the perspiration is by any means in- 
creased, and several drops tnat were insensi- 
ble when separate, are united together and con- 
densed by the external air, they form upon 
the skin small, but visible, drops called sweat.* 
This particularly happens after much exercise, 
or whatever occasions an increased determin- 
ation of fluids to the surface of the body ; a 
greater quantity of perspirable matter being 
in such cases carried through the passages that 
are destined to convey it off. 

It has been disputed, indeed, whether the 
insensible perspiration and sweat are to be 
considered as one and the same excretion, dif- 
fering only in degree; or whether they are 
two distinct excretions derived from different 
sources. In support of the latter opinion, it 
has been alleged, that the insensible perspi- 
ration is agreeable to nature, and essential to 
health, whereas sweat may be considered as a 
species of disease. But this argument proves 
nothing ; and it seems probable, that both the 
insensible vapour and the sweat are exhaled 
in a similar manner, though they differ in 
quantity, and probably in their qualities ; the 
former being more limpid, and seemingly less 
impregnated with salts than the latter : at any 
rate we may consider the skin as an emuncto- 
ry through which the redundant water, and 

* Lieuwenhoeck asserts that one drop of sweat is formed by 
the conflux of fifteen drops of perspirable vapour. 



Of the Integuments, &c. 165 

sometimes the other more saline parts of the 
blood, are carried off. But the insensible per- 
spiration is not confined to the skin only — a 
great part of what we are constantly throwing 
off in this way is from the lungs. The quantity 
of fluid exhaled from the human body by this 
insensible perspiration is very considerable. 
Sanctorius* an Italian physician, who indefati- 
gably passed a great many years in a series of sta- 
tical experiments, demonstrated long ago what 
has been confirmed by later observations, that 
the quantity of vapour exhaled from the skin 
and from the surface of the lungs, amounts 
nearly to 5-8ths of the aliment we take in. So 
that if in the warm climate of Italy a person eats 
and drinks the quantity of eight pounds in the 
course of a day, five pounds of it will pass off 
by insensible perspiration, while three pounds 
only will be evacuated by stool, urine, saliva, 
&c. But in countries where the degree of 
cold is greater than in Italy, the quantity of 
perspired matter is less ; in some of the more 
northern climates, it being found not to equal 
the discharge by urine. It is likewise observ- 

* The insensible perspiration is sometimes distinguished by 
the name of this physician, who was born in the territories of 
Venice, and was afterwards a professor in the university of Pa- 
dua. After estimating the aliment lie took in, and the sensible 
secretions and discharges, he was enabled to ascertain with great 
accuracy the weight or quantity of insensible perspiration by 
means of a statical chair which he contrived for this purpose; and 
from his experiments, which were conducted with great industry 
and patience, he was led to determine what kinds of solid or li- 
quid aliment increased or diminished it. From these experi- 
ments he formed a system, which he published at Venice in 1614, 
in the form of aphorisms, under the title of " Ars dc Medicina 
Statical' 



165 Of the Integuments, &c. 

ed to vary according to the season of the 
year, and according to the constitution, age, 
sex, diseases, diet, exercise, passions, &c. of 
different people. 

From what has been said on this subject, it 
will be easily conceived, that this evacuation 
cannot be either much increased or diminish- 
ed in quantity without affecting the health. 

The perspirable matter and the sweat are in 
some measure analogous to the urine, as ap- 
pears from their taste and saline nature.* And 
it is worthy of observation, that when either 
of these secretions is increased in quantity, 
the other is diminished ; so that they who per- 
spire the least, usually pass the greatest quan- 
tity of urine, and vice versa. 

6. Of the Nails. 

The nails are of a compact texture, hard 
and transparent like horn. Their origin is 
still a subject of dispute. Malpighi supposed 
them to be formed by a continuation of the 
papilla of the skin : Ludwig, on the other hand, 
maintained, that they were composed of the 
extremities of blood-vessels and nerves ; both 
these opinions are now deservedly rejected. 

They seem to possess many properties in 
common with the cuticle ; like it they are nei- 
ther vascular nor sensible, and when the cuti- 

* Minute chrystals have been observed to shoot upon the 
clothes of men who work in glass-houses. Haller Elem. Phys. 



Of the Integuments, &c. 167 

cle is separated from the true skin by macera- 
tion or other means, the nails come away with 
it. 

They appear to be composed of different 
layers, of unequal size, applied one over the 
other. Each layer seems to be formed of lon- 
gitudinal fibres. 

In each nail we may distinguish three parts, 
viz. the root, the body or middle, and the ex- 
tremity. The root is of a soft, thin, and white 
substance, terminating in the form of a cres- 
cent ; the epidermis adheres very strongly to 
this part; the body of the nail is broader, red- 
der, and thicker, and the extremity is of still 
greater firmness. 

The nails increase from their roots, and not 
from their upper extremity. 

Their principal use is to cover and defend 
the ends of the fingers and toes from external 
injury. 

7. Of the Hair. 

The hairs, which from their being general- 
ly known do not seem to require any definit.on, 
arise from distinct capsules or bulbs seated in 
the cellular membrane under the skin.* Some 

* Malpighi, and after him the celebrated Ruysch, supposed 
the hairs to be continuations of nerves, being of opinion that 
they originated from the papilla: of the skin, which they consi- 
dered as nervous; and as a corroborating proof of what they 
advanced, they argued the pain we feel in plucking them out ; 
but later anatomists seem to have rejected this doctrine, and con- 
sider the hairs as particular bodies, not arising from the papillae 
(for in the parts where the papillce abound most there are n 
hairs,) but from bulbs or capsules, which are peculiar to them. 



168 Of the Integuments, &c. 

of these bulbs inclose several hairs. They 
may be observed at the roots of the hairs 
which form the beard or whiskers of a cat. 

The hairs, like the nails, grow only from 
below by a regular propulsion from their root, 
where they receive their nourishment. Their 
bulbs, when viewed with a microscope, are 
found to be of various shapes. In the head 
and scrotum they are roundish ; in the eye- 
brows they are oval ; in the other parts of the 
body they are nearly of a cylindrical shape. 
Each bulb seems to consist of two membranes, 
between which there is a certain quantity of 
moisture. Within the bulb the hair separates 
into three or four fibrillae ; the bodies of the 
hairs, which are the parts without the skin, 
vary in softness and colour according to the 
difference of climate, age, or temperament of 
body.* 

Their general use in the body does not seem 
to be absolutely determined ; but hairs in par- 
ticular parts, as on the eye-brows and eye-lids, 
are destined for particular uses, which will be 
mentioned when those parts are described. 

8. Of the Cellular Membrane and Fat. 

The cellular membrane is found to invest 
the most minute fibres we are able to trace ; so 
that by modern physiologists, it is very pro- 

* The hairs differ likewise from each other, and may not be 
improperly divided into two classes ; one of which may include 
the hair of the head, chin, pubes, anJ axillae ; and the other, the 
softer hairs, which arc to be observed almost every where on 
the surface of die body. 



Of the Integuments, &c. 169 

perly considered as the universal connecting 
medium of" every part of the body. 

It is composed of an infinite number of mi- 
nute cells united together, and communicating 
with each other. The two diseases peculiar 
to this membrane are proofs of such a commu- 
nication ; for in the emphysema all its cells are 
filled with air, and in the anasarca they are 
universally distended with water. Besides these 
proofs of communication from disease, a fa- 
miliar instance of it may be observed among 
butchers, who usually puncture this membrane, 
and by inflating it with air add to the good ap- 
pearance of their meat. 

The cells of this membrane serve as re- 
servoirs to the oily part of the blood or Fat, 
which seems to be deposited in them, either 
by transudation through the coats of the ar- 
teries, that ramify through these cells, or by 
particular vessels, continued from the ends of 
arteries. These cells are not of a glandular 
structure, as Malpighi and others after him 
have supposed. The fat is absorbed and car- 
ried back into the system by the lymphatics. 
The great waste of it in many diseases, par- 
ticularly in the consumption, is a sufficient 
proof that such an absorption takes place. 

The fulness and size of the body are in a 
great measure proportioned to the quantity of 
fat contained in the cells of this membrane. 

In the living body it seems to be a fluid oil, 
which concretes after death. In graminivo- 
rous animals, it is found to be of a firmer con- 
sistence than in man. 

Y 



170 Of the Muscles. 

The fat is not confined to the skin alone, 
being met with every where in the interstices 
of muscles, in the omentum, about the kid- 
neys, at the basis of the heart, in the orbits, 
&c. 

The chief uses of the fat. seem to be to 
afford moisture to all the parts with which it 
is connected ; to facilitate the action of the 
muscles ; and to add to the beauty of the body, 
by making it every where smooth and equal. 

Sect. II. Of the Muscles. 



The muscles are the organs of motion. The 
parts that are usually included under this name 
consist of distinct portions of flesh, suscepti- 
ble of contraction and relaxation ; the motions 
of which in a natural and healthy state, are 
subject to the will, and for this reason they 
are called voluntary muscles. But besides 
these, there are other parts of the body that 
owe their power of contraction to their mus- 
cular fibres ; thus the heart is of a muscular 
texture, forming what is called a hollow mus- 
cle ; and the urinary bladder, stomach, intes- 
tines, &c. are enabled to act upon their con- 
tents, merely because they are provided with 
muscular fibres. These are called involuntary 
muscles, because their motions are not depen- 
dent on the will. The muscles of respiration, 
being in some measure influenced by the wilh 
are said to have a mixed motion. 



Of the Muscles. 171 

The names by which the voluntary muscles 
are distinguished, are founded on their size, 
figure, situation, use, or the arrangement ot 
their fibres, or their origin and insertion. But 
besides these particular distinctions, there are 
certain general ones that require to be noticed. 

Thus, if the fibres of a muscle are placed 
parallel to each other in a straight direction, 
they form what are styled a rectilinear muscle ; 
if the fibres cross and intersect each other, they 
constitute a compound muscle ; a radiated one, 
if the fibres are disposed in the manner of 
rays; or a pe uniform muscle, if, like the plume 
of a pen, they are placed obliquely with re- 
spect to the tendon. 

Muscles that act in opposition to each other, 
are called antagonists ; thus every extensor 
muscle has a flexor for its antagonist, and vice 
versa. Muscles that concur in the same ac- 
tion are styled conger eres. 

The muscles being attached to the bones, 
the latter may be considered as levers that are 
moved in different directions by the contrac- 
tion of those organs. 

The end of a muscle which adheres to the 
most fixed part is usually called the origin, 
and that which adheres to the more moveable 
part, the insertion, of the muscle. 

In every muscle we may distinguish two 
kinds of fibres ; the one soft, of a red colour, 
sensible and irritable, called/fos/zy fibres ; the 
other of a firmer texture, of a white glisten- 
ing colour, insensible, without irritability or 
the power of contracting, and named tendinous 



172 Of the Muscles. 

iibres. They arc occasionally intermixed ; but 
the fleshy fibres generally prevail in the belly 
or middle part of a muscle, and the tendi- 
nous ones in the extremities. If these tendi- 
nous fibres are formed into a round slender 
chord, they form what is called the tendon of 
the muscle ; on the other hand, if they are 
spread into a broad flat surface, the extremity 
of the muscle is styled aponeurosis. 

The tendons of many muscles, especially 
when they are long and exposed to pressure or 
friction in the grooves formed for them in the 
bones, are surrounded by a tendinous sheath 
or fascia, in which wc sometimes find a small 
mucous sac or bursa mucosa, which obviates 
a,ny inconvenience from friction. Sometimes 
we find whole muscles, and even several mus* 
cles, covered by a fascia of the same kind, 
that affords origin to many of their fibres, dip- 
ping down between them, adhering to the 
ridges of bones, and thus preventing them 
from swelling too much when in action. The 
most remarkable instance of such a covering 
is the fascia lata of the thigh. 

Each muscle is inclosed by a thin covering 
of cellular membrane, which has been some- 
times improperly considered as peculiar to the 
muscles, and described under the name of pro- 
pria membrana musculosa. This cellular co- 
vering dips down into the substance of the 
muscle, connecting and surrounding the most 
minute fibres we are able to demonstrate, and 
affording a support to their vessels and nerves. 

Lieuwenhoeck fancied he had discovered, by 



Of the Muscles, 173 

means of his microscope, the ultimate division 
of a muscle, and that he could point out the sim- 
ple fibre, which appeared to him to be an hun- 
dred times less than a hair ; but he was after- 
wards convinced how much he was mistaken 
on this subject, and candidly acknowledged, 
that what he had taken for a simple fibre was 
in fact a bundle of fibres. 

It is easy to observe several of these fasci- 
culi or bundles in a piece of beef, in which, 
from the coarseness of its texture, they are 
very evident. 

The red colour which so particularly distin- 
guishes the muscular or fleshy parts of ani- 
mals, is owing to an infinite number of blood- 
vessels that are dispersed through their sub- 
stance. When we macerate the fibres of a 
muscle in water, it becomes of a white colour 
like all other parts of the body divested of 
their blood. The blood-vessels are accompa- 
nied by nerves, and they are both distributed in 
such abundance to these parts, that in endea- 
vouring to trace the course of the blood-ves- 
sels in a muscle, it would appear to be formed 
altogether by their ramifications ; and in an 
attempt to follow the branches of its nerves, 
they would be found to be equal in propor- 
tion. 

If a muscle is pricked or irritated, it im- 
mediately contracts. This is called its irrita- 
ble principle ; and this irritability is to be con- 
sidered as the characteristic of muscular fibres, 
and may serve to prove their existence in parts 
that are too minute to be examined by the eye. 



174 Of the Muscles. 

This power, which disposes the muscles to 
contract when stimulated, independent of the 
will, is supposed to be inherent in them ; and 
is therefore named vis insita. This property 
is not to be confounded with elasticity, which 
the membranes and other parts of the body 
possess in a greater or less degree in common 
with the muscles ; nor with sensibility, for 
the heart, though the most irritable, seems to 
be the least sensible of any of the muscular 
parts of the body. 

After a muscular fibre has contracted, it 
soon returns to a state of relaxation, till it 
is excited afresh, and then it contracts and re- 
laxes again. We may likewise produce such 
a contraction, by irritating the nerve leading 
to a muscle, although the nerve itself is not 
affected. 

This principle is found to be greater in 
small than in large, and in young than in old, 
animals. 

In the voluntary muscles these effects of con- 
traction and relaxation of the fleshy fibres are 
produced in obedience to the will, by what may 
be called the vis nervosa, a property that is 
not to be confounded with the vis insita. As 
the existence of a vis insita different from a 
vis nervea, was the doctrine taught by Doctor 
Haller in his Elem. PJiys. but is at present 
called in question by several, particularly Doc- 
tor Monro, we think it necessary to give a few 
objections, as stated in his Observations on 
the Nervous System: 



Of the Muscles. 175 

" The chief experiment (says the Doctor) 
which seems to have led Dr. Haller to this 
opinion, is the well known one, that the heart 
and other muscles, after being detached from 
the brain, continue to act spontaneously, or 
by stimuli may be roused into action for a con- 
siderable length of time ; and when it cannot 
be alleged, says Dr. Haller, that the nervous 
fluid is by the mind, or otherwise, impelled 
into the muscle. 

U That in this instance, we cannot compre- 
hend by what power the nervous fluid or ener- 
gy can be put in motion, must perhaps be 
granted: But has Dr. Haller given a better 
explanation of the manner in which his sup- 
posed vis insita becomes active ? 

" If it be as difficult to point out the cause 
of the action of the vis insita as that of the 
action of the vis nervea, the admission of 
that new power, instead of relieving, would 
add to our perplexity. 

" We should then have admitted, that two 
causes of a different nature were capable of 
producing exactly the same effect ; which is 
not in general agreeable to the laws of nature. 

" We should find other consequences arise 
from such an hypothesis, which tend to weak- 
en the credibility of it. For instance, if in a 
sound animal the vis nervea alone produces 
the contraction of the muscles, we will ask 
what purpose the vis insita serves ? If both 
operate, are we to suppose that the vis nervea, 
impelled by the mind or living principle, gives 
the order, which the vis insita executes, and 



176 Of the Muscles. 

that the nerves are the internuntii ; and so ad- 
mit two wise agents employed in every the most 
simple action ? But instead of speculating far- 
ther, let us learn the effect of experiments, 
and endeavour from these to draw plain conclu- 
sions. 

" 1. When I poured a solution of opium in 
water under the skin of the leg of a frog, the 
muscles, to the surface of which it was appli- 
ed, were very soon deprived of the power of 
contraction. In like manner, when I poured 
this solution into the cavity of the heart, by 
opening the vena cava, the heart was almost 
instantly deprived of its power of motion, whe- 
ther the experiment was performed on it fixed 
in its place, or cut out of the body. 

" 2. I opened the thorax of a living frog; 
and then tied or cut its aorta, so as to put a 
stop to the circulation of its blood. 

" I then opened the vena cava, and poured 
the solution of opium into the heart ; and 
found, not only that this organ was instantly 
deprived of its powers of action, but that in a 
few minutes the most distant muscles of the 
limbs were extremely weakened. Yet this 
weakness was not owing to the want of circu- 
lation, for the frog could jump about for more 
than an hour after the heart was cut out. 

" In the first of these two experiments, we 
observed the supposed vis insita destroyed by 
the opium; in the latter, the vis nervea; for it 
is evident that the limbs were affected by the 
sympathy of the brain, and of the nervous 



Of the Muscles. 177 

system in general, with the nerves of the 
heart. 

3. When the nerve of any muscle is first 
divided by a transverse section, and then 
burnt with a hot iron, or punctured with a nee- 
dle, the muscle in which it terminates con- 
tracts violently, exactly in the same manner as 
when the irritation is applied to the fibres of 
the muscle. But when the hot iron, or nee- 
dle, is confined to the nerve, Dr. Haller him- 
self must have admitted, that the vis nervea, 
and not the vis insita, was excited. But here 
I would ask two questions. 

" First, Whether we do not as well under- 
stand how the vis nervea is excited when irri- 
tation is applied to the muscle as when it is ap- 
plied to the trunk of the nerve, the impelling 
power of the mind seeming to be equally 
wanting in both cases ? 

" Secondly, If it appears that irritation ap- 
plied to the trunk of a nerve excites the vis 
nervea, why should we doubt that it can equal- 
ly well excite it when applied to the small and 
very sensible branches and terminations of the 
nerve in the muscle ? 

" As, therefore, it appears that the suppos- 
ed vis insita is destroyed or excited by the 
same means as the vis nervea ; nay, that when, 
by the application of opium to the heart of a 
frog, after the aorta is cut and the circulation 
interrupted, we have destroyed the vis insita, 
the vis nervea is so much extinguished, that 
the animal cannot act with the distant muscles 

Z 



178 Of the Muscles. 

of the limb; and that these afterward grow 
very torpid, or lose mucn of their supposed 
vis insita ; it seems elearly to follow, that there 
is no just ground for supposing that any other 
principle produces the contraction of a mus- 
cle." 

The vis nervosa, or operation of the mind, 
if we may so call it, by which a muscle is 
brought into contraction, is not inherent in the 
muscle like the vis insita ; neither is it perpe- 
tual, like this latter property. After long con- 
tinued or violent exercise, for example, the vo- 
luntary muscles become painful, and at length 
incapable of further action ; whereas the heart 
and other involuntary muscles, the motions of 
which depend solely on the vis insita, continue 
through life in a constant state of action, with- 
out any inconvenience or waste of this inherent 
principle. 

The action of the vis nervosa on the volun- 
tary muscles, constitutes what is called mus- 
cular motion ; a subject that has given rise to 
a variety of hypotheses, many of them inge- 
nious, but none of them satisfactory. 

Borelli and some others have undertaken to 
explain the cause of contraction, by suppos- 
ing that every muscular fibre forms as it were ' 
a chain of very minute bladders, while the 
nerves which are distributed through the mus- 
cle, bring with them a supply of animal spi- 
rits, which at our will fill these bladders, and 
by increasing their diameter in width, shorten 
them, and of course the whole fibre. 



Of the Muscles. 179 

Borelli supposes these bladders to be of a 
rhomboidal shape ; Bernoulli on the other 
hand contends that they are oval. Our coun- 
tryman, Covvper, fancied he had filled them 
with mercury ; the cause of this mistake was 
probably owing to the mercury's insinuating 
itself into some of the lymphatic vessels. The 
late ingenious Mr. Elliot undertook to account 
for the phenomena of muscular motion on prin- 
ciples very different from those just now men- 
tioned. He supposed that a dephlogisticated 
state of the blood is requisite for muscular ac- 
tion, and that a communication of phlogiston to 
the blood is a necessary effect of such action. 
We know that the muscular fibre is shorten- 
ed, and that the muscle itself swells when in 
action ; but how these phenomena are produc- 
ed, we are unable to determine. We likewise 
know that the nerves are essential to muscu- 
lar motion ; for upon dividing or making a li- 
gature round the nerve leading to a muscle, 
the latter becomes incapable of motion. A li- 
gature made on the artery of a muscle pro- 
duces a similar effect; a proof this, that a re- 
gular supply of blood is also equally necessa- 
ry to muscular motion. The cause of palsy 
is usually not to be sought for in the muscle 
affected, but in the nerve leading to that mus- 
cle, or in that part of the brain or spinal mar- 
row from which the nerve derives its origin. 



180 Of the Muscles. 



Of the particular Muscles. 

As the enumeration and description of the 
particular muscles must be dry and unenter- 
taining to the generality of readers, yet can- 
not be altogether omitted in a work of this 
nature, it appeared eligible to throw this part 
of the subject into the form of a table ; in 
which the name, origin, insertion, and princi- 
pal use of each muscle, will be found describ- 
ed in few words, and occasionally its etymolo- 
gy when it is of Greek derivation or difficult 
to be understood. 



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204 Of the Muscles. 



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230 Of the Muscles. 



EXPLANATION of PLATES XXIII. and 
XXIV. 



Plate XXIII. 



Fig. 1. The Muscles immediately under 
the common teguments on the anterior part of 
the body are represented on the right side ; 
and on the left side the Muscles are seen 
which come in view when the exterior ones 
are taken away. 

A, The frontal muscle. B, The tendinous 
aponeurosis which joins it to the occipital 
hence both named occipito-frontalis. C, Attol 
lens aurem. D, The ear. E, Anterior au 
ris. F F, Orbicularis palpebrarum. G, Le 
vator labii superioris alaeque nasi. H, Leva 
tor anguli oris. I, Zygomaticus minor. K 
Zygomaticus major. L, Masseter. M, Or 
bicularis oris. N, Depressor labii inferioris 
O, Depressor anguli oris. P, Buccinator 
QQ, Platysma myoides. RR, Sterno-cleido 
mastoidaeus. S, Part of the trapezius. T 
Part of the scaleni. 

Superior Extremity — U, Deltoides. V 
Pectoralis major- W, Part of the latissimus 
dorsi. X X, Biceps flexor cubiti. Y Y, Part 
of the brachialis externus. Z Z, The begin- 
ning of the tendinous aponeurosis (from the 
biceps), which is spread over the muscles of 



n- ^c - a-"i*» n 







Of the Muscles. 231 

the fore-arm. a a, Its strong tendon inserted 
into the tubercle of the radius, b b, Part of 
the brachialis internus- c, Pronator radii te- 
res, d, Flexor carpi radialis- e, Part of the 
flexor carpi ulnaris- f, Palmaris longus. g, 
Aponeurosis palmaris- 3, Palmaris brevis. 1, 
Ligamentum carpi annulare. 2 2, Abductor 
minimi digiti- h, Supinator radii longus. i, 
The tendons of the thumb- k, Abductor pol- 
licis. 1, Flexor pollicis longus. m m, The 
tendons of the flexor sublimis perforatus, 
profundus perforans, and lumbricales — The 
sheaths are entire in the right hand, — in the 
left cut open to show the tendons of the flex- 
or profundus perforating the sublimis. 

Muscles not referred to — in the left supe- 
rior extremity — n, Pectoralis minor, seu ser- 
ratus anticus minor- o, The two heads of 
(x x) the biceps, p, Coraco-brachialis. q q, 
The long head'of the triceps extensor cubiti. 
rr, Teres major- ((, Subscapulars. 1 1, Ex- 
tensores radiales. u, Supinator brevis. v, 
The cut extremity of the pronator teres, w, 
Flexor sublimis perforatus. x, Part of the 
flexor profundus, y, Flexor pollicis longus. 
z, Part of the flexor pollicis brevis- 4, Ab- 
ductor minimi digiti. 5, The four lumbri- 
cales- 

Trunk. — 6, Serrated extremities of the ser- 
ratus anticus major- 7 7, Obliquus externus 
abdominis. 8 8, The linea alba- 9, The um- 
bilicus. 10, Pyramidalis. 1111, The sper- 
matic cord. On the left side it is covered by 



232 Of the Muscles, 

the cremaster. 12 12, Rectus abdominis. 13, 
Obliquus interims- 14 14, &c. Intercostal 
muscles. 

Inferior Extremities — a a, The graci. 
lis. b b, Parts of the triceps, c c, Pectialis. 
dd, Psoas magnus- e e, Iliacus internus. f t 
Part of the glutaeus medius- ,§-, Part of the 
gluteus minimus, /z, Cut extremity of the 
rectus cruris, i't, Vastus externus, k, Ten- 
don of the rectus cruris. / /, Vastus internus. 
* Sartorius muscle. ** Fleshy origin of the 
tensor vaginae faemoris or membranosus. Its 
tendinous aponeurosis covers (i) the vastus 
externus in the right side, m m, Patella, n n 
Ligament or tendon frorn it to the tibia, o 
Rectus cruris. />, Crurxus. q q, The tibia 
r r, Part of the Gemellus or gastrocnemius ex 
ternus.* ///, Part of the soleus or gastroc 
nemius internus. f, Tibialis amicus, w, Ti 
foialis posticus, v v, Peronaei muscles, ww 
Extensor longus digitorum pedis, x x, Ex 
tensor longus pollicis pedis- y, Abductor pol 
licis pedis. 

Fig- 2- The Muscles, Glands, he. of the 
Left Side of the face and neck, after the 
common Teguments and Platysma myoides 
have been taken off. 

a, The frontal muscle, b, Temporalis and 
temporal artery, c, Orbicularis palpebrarum, 
d, Levator labii superioris alseque nasi, e, 
Levator anguli oris, f, Zygomaticus. g, De- 
pressor labii inferioris. h, Depressor anguli 



Of the Muscles. 23 ;> 

oris, i, Buccinator, k, Masseter. 1 1, Paro- 
tid gland- m, Its duct- n, Sterno-cleido-mas- 
tokheus. o, Part of the trapezius, p, Sterno- 
hyoidoeus. q, Sterno-thyroidaeus. r, Omo- 
hyoidacus. F, Levator scapube- 1 1, Scaleni. 
u, Part of the splenius. 

Fig. 3. The Muscles of the Face and Neck 
in view after the exterior ones are taken 
away. 

a a, Corrugator supercilik b, Temporalis- 

c, Tendon of the levator palpebral superioris- 

d, Tendon of the orbicularis palpebrarum, e, 
Masseter. f, Buccinator, g, Levator anguli 
oris, h, Depressor labii superioris alseque na- 
si, i, Orbicularis oris- k, Depressor anguli 
Oris. 1, Muscles of the os hyoides. m, Ster- 
no-cleido-mastoidceus. 

Fig. 4- Some of the Muscles of the Os Hy- 
oides and Submaxillary Gland. 

a, Part of the masseter muscle- b, Poste- 
rior head of the digrastic. c, Its anterior 
head, d d, Sterno-hyoidaeus- e, Omo-hyoi- 
daeus. f, Stylo-hyoidseus. g, Submaxillary 
gland in situ. 

Fig. 5. The Submaxillary Gland and Duct. 
a, Musculus mylo-uyoidaeus. b, Hyo-glos- 
sus. c, Submaxillary gland extra situ, d, Its 
duct. 

Plate XXIV. 

Fig. 1. The Muscles immediately under 
the common teguments on the posterior part 

O g 



234 Of the Muscles. 

of the body, are represented in the right side; 
and on the left side the Muscles are seen 
which come in view when the exterior ones 
are taken away. 

Head* — A A, Occipito-frontalis. B, Attol- 
lens aurem. C, Part of the orbicularis palpe- 
brarum. D, Masseter. E, Pterygoidaeus in- 
ter nus. 

Trunk. — Right side. FFF, Trapezius seu 
cucullaris. G G G G, Latissimus dorsi. H, 
Part of the obliquus externus abdominis. 

Trunk. — Left side.. I, Splenius- K, Part 
pf the complexus. L, Levator scapulas. M, 
Rhomboides. N N, Serratus posticus inferi- 
or. O, Part of the longissimus dorsi. P, 
Part of the sacro-lumbalis. Q, Part of the 
semi-spinalis dorsi. R, Part of the serratus 
amicus major. S y Part of the obliquus in- 
ternus abdominis. 

Superior Extremity. — Right side. T, 
Deltoides. U, Triceps extensor cubiti. V, 
Supinator longus. W W, Extensores carpi 
radialis longior and brevior- X X, Extensor 
carpi ulnaris- Y Y, Extensor digitorum com- 
munis. Z, Abductor indicts, 12 3, Exten- 
sores pollicis. 

Superior Extremity. — Left side, a, Su- 
pra spinatus. b, Infra-spinatus. c, Teres 
minor, d, Teres major, e, Triceps extensor 
cubiti. f f, Extensores carpi radiales. g, Su- 
pinator brevis. h, Indicator. 12 3, Exten- 
sores pollicis. i, Abductor minimi digiti. k, 
Interossei. 

Inferior Extremity. — Right side. 1, Glu- 
teus maximus. m, Part of the Glutaeus me- 



Of the Muscles. 235 

dius. 11, Tensor vaginoe femoris. o, Graci- 
lis, p p, Abductor femoris magnus. q, Part 
of the vastus iuternus. r, Semimembrano- 
sus, s, Semitendinosus- t, Long head of the 
biceps flexor cruris, u u, Gastrocnemius ex- 
ternus seu gemellus, v, Tendo Achillis. w, 
Soleus seu gastrocnemius internus. x x, Pe- 
ronaeus longus and brevis. y, Tendons of the 
flexor longus digitorum pedis ; — and under 
them * flexor brevis digitorum pedis- z, Ab 
ductor minimi digiti pedis. 

Inferior Extremity. — Left side, m, », 
o, />, </, r, s, /, <y, w w, x x, y, z, Point the 
same parts as in the right side. «, Pyrifor- 
mis. b Z>, Gemini, c c, Obturator internus. 
<7, Quadratus femoris. e, Coccygaeus. j\ The 
short head of the biceps flexor cruris- gg, 
Plantaris. A, Poplitaeus. i, Flexor longus 
pollicis pedis. 

Fig. 2. The Palm of the Left Hand after the 
common Teguments are removed, to show 
the Muscles of the Fingers. 

a, Tendon of the flexor carpi radialis. b, 
Tendon of the flexor carpi ulnaris. c, Ten- 
dons of the flexor sublimis perforatus, pro- 
fundus perforans and lumbricales. d, Ab- 
ductor pollicis. e e, Flexor pollicis longus. 
f, Flexor pollicis brevis. g, Palmaris brevis- 
h, Abductor minimi digiti. i, Ligamentum 
carpiannulare. k, A probe put under the ten- 
dons of the flexor digitorum sublimis ; which 
are perforated by 1, the flexor digitorum pro- 
fundus, m m m m, Lumbricales. n, Abduc- 
tor pollicis. 



236 Of the Abdomen. 

Fig 3. A Fore- view of the foot and Tendons 
of the Flexores Digitorum. 

a, Cut extremity of the tendo Achillis. b 
Upper part of the astragalus, c, Os calcis. 

d, Tendon of the tibialis amicus, e, Tendon 
of the extensor pollicis longus. f, Tendon of 
the peronxus brevis. g, Tendons of the flex- 
or digitorum longus, with the nonus Vesalii. 
h h, The whole of the flexor digitorum bre- 
vis. 

Fig. 4. Muscles of the Anus. 

a a, An out line of the buttocks, and upper 
part of the thighs, b, The testes contained 
in the scrotum, c c, Sphincter ani. d, Anus. 

e, Levator ani. f f, Erector penis, g g, Ac- 
celerator urinse. h, Corpus cavernosum ure- 
thra?. 

Fig. 5. Muscles of the Penis. 
a a, b, d, e e, f f, h, point the same as in 
fig. 4. c, Sphincter ani. g g, Transversalis 
penis. 



Part III. OF THE ABDOMEN, OR 
LOWER BELLY. 

THE abdomen or lower belly, extends from 
the lower extremity of the sternum, or 
the hollow, usually called the pit of the sto- 
mach, and more properly scrobiculus cordis, to 
the lower part of the trunk- 



Of the Abdomen. 237 

It is distinguished into three divisions call- 
ed regions ; of these the upper one, which is 
called the epigastric region, begins immediate- 
ly under the sternum, and extends to within 
two fingers breadth ot" the navel, where the 
middle or umbilical region begins, and reaches 
to the same distance below the navel. The 
third, which is called the hypogastric, includes 
the rest of the abdomen, as far as the os pu- 
bis. 

Each of these regions is subdivided into 
three others ; two of which compose the sides, 
and the other the middle part of each region. 
'1 he middle part of the upper region is call- 
ed epigastrium, and its two sides hypochondria. 
The middle part of the next region is the um- 
bilical region, properly so called, and its two 
sides are the flanks, or iliac regions. Lastly, 
the middle part of the lower region retains the 
name of hypogastrium, and its sides are call- 
ed inguina or groins. The back part of the 
abdomen bears the name of lumbar region- 

These are the divisions of the lower belly, 
which are necessary to be held in remem- 
brance, as they frequently occur in surgical 
and anatomical writing. We will now proceed 
to examine the contents of the abdomen ; and 
after having pointed out the names and ar- 
rangement of the several viscera contained in 
it, describe each of them separately- 
After having removed the skin, adipose 
membrane, and abdominal muscles, wc disco- 
ver the peritonceum or membrane that enve- 
lopes all the viscera of the lower belly- This 
being opened, the first part that presents itself 



238 Of the Abdomen. 

is the omentum or cawi, floating on the sur- 
face of the intestines, which are likewise seen 
every where loose and moist, and making a 
great number of circumvolutions through the 
whole cavity of the abdomen. The stomach 
is placed in the epigastrium, and under the 
stomach is the pancreas. The liver fills the 
Tight hypochondrium, and the spleen is situ- 
ated in the left. The kidneys are seen about 
the middle of the lumbar region, and the uri- 
nary bladder and parts of generation are seat- 
ed in the lower division of the belly. 

Sect. I. Of the Peritoneum. 

The peritonaeum is a strong simple mem- 
brane, by which all the viscera of the abdo- 
men are surrounded, and in some measure 
supported. Many anatomical writers, particu- 
larly Winslow, have described it as being com- 
posed of two distinct membranous laminae; but 
their description seems to be erroneous. What 
perhaps appeared to be a second lamina, being 
found to be simply a cellular coat, which sends 
off productions to the blood-vessels passing 
out of the abdominal cavity. The aorta and 
vena cava likewise derive a covering from the 
same membrane, which seems to be a part of 
the cellular membrane we have already de- 
scribed. 

The peritoneum, by its productions and re- 
duplications, envelopes the greatest part of 
the abdominal viscera. It is soft, and capable 
of considerable extension ; and is kept smooth 
and moist by a vapour which is constantly ex- 



Of the Abdomen. 239 

haling from its inner surface, and is returned 
again into the circulation by the absorbents. 

This moisture not only contributes to the 
softness of the peritonaeum, but prevents the 
attrition, and other ill effects which would 
otherwise probably be occasioned, by the mo- 
tion of the viscera upon each other. 

When this fluid is supplied in too great a 
quantity, or the absorbents become incapable 
of carrying it off, it accumulates, and consti- 
tutes an ascites or dropsy of the belly ; and 
when by any means the exhalation is discon- 
tinued, the peritonaeum thickens, becomes dis- 
eased, and the viscera are sometimes found 
adhering to each other. 

The peritonaeum is not a very vascular 
membrane. In a sound state it seems to be 
endued with little or no feeling, and the nerves 
that pass through it appear to belong to the 
abdominal muscles. 

Sect. II. Of the Omentum. 

The omentum, epiploon, or cawl, is a dou- 
ble membrane, produced from the peritonaeum, 
It is interlarded with fat, and adheres to the 
stomach, spleen, duodenum, and colon ; from 
thence hanging down loose and floating on the 
surface of the intestines. Its size is different 
in different subjects. In some it descends as 
low as the pelvis, and it is commonly longer at 
the left side than the right. 

This part, the situation of which we have 
just now described, was the only one known 
to the ancients under the name of epiploon ; 



24© Of the Abdomen. 

but at present we distinguish three omenta, 
viz. omentum magnum colico gastricum, onirti- 
turn parvum hepatico gastricum, and omentum 
colicum. They all agree in being formed of 
two very delicate lamina?, separated by a thin 
layer of cellular membrane. 

The omentum magnum colico gastricum, of 
which we have already spoken, derives its ar- 
teries from the splenic and hepatic. Its veins 
terminate in the vena portae. Its nerves, which 
are very few, come from the splenic and he- 
patic plexus. 

The omentum parvum hepatico gastricum, 
abounds less with fat than the great epiploon. 
It begins at the upper part of the duodenum, 
extends along the lesser curvature of the sto- 
mach as far as the oesophagus, and terminates 
about the neck of the gall-bladder, and behind 
the left ligament of the liver, so that it covers 
the lesser lobe; near the beginning of which 
we may observe a small opening, first describ- 
ed by Winslow, through which the whole 
pouch may easily be distended with air.* The 
vessels of the omentum parvum are derived 
chiefly from the coronary stomachic arteries 
and veins. 

The omentum colicum begins at the fore 
part of the ccecum and right side of the colon. 
It appears as a hollow conical appendage to 
these intestines, and usually terminates at the 
back of the omentum magnum- It seems to 

* This membranous bag, though exceedingly thin and trans- 
parent, is found capable of supporting mercury, thrown into 't 
by the same channel. 



Of the Abdomen. 241 

be nothing more than a membranous coat of 
the cecum and colon, assuming a conical shape 
when distended with air. 

The uses of the omentum are not yet satis- 
factorily determined. Perhaps by its softness 
and looseness it may serve to prevent those 
adhesions of the abdominal viscera, which 
have been found to take place when the fat 
of the omentum has been much wasted. Some 
authors have supposed, that it assists in the 
preparation of bile ; but this idea is founded 
merely on conjecture. 

Sect. III. Of the Stomach. 

The stomach is a membranous and muscu- 
lar bag, in shape not unlike a bag-pipe, lying 
across the upper part of the abdomen, and in- 
clining rather more to the left than the right 
side. 

It has two orifices, one of which receives 
the end of the oesophagus, and is called the 
cardia, and sometimes the left and upper ori- 
fice of the stomach ; though its situation is not 
much higher than the other, which is styled 
the right and inferior orifice, and more com- 
monly the pylorus; both these openings are 
more elevated than the body of the stomach. 

The aliment passes down the oesophagus in- 
to the stomach through the cardia, and after 
having undergone the necessary digestion, 
passes out at the pylorus where the intesti- 
nal canal commences. 

The stomach is composed of four tunics or 
coats, which are so intimately connected toge- 

H h 



242 Of the Abdomen. 

ther that it requires no little dexterity in the 
anatomist to demonstrate them. The exterior 
one is membranous, being derived from the 
peritonaeum. — The second is a muscular tu- 
nic, composed of fleshy fibres which are in the 
greatest number about the two orifices. — The 
third is called the nervous coat, and within 
this is the villous or velvet-like coat which 
composes the inside of the stomach. 

The two last coats being more extensive 
than the two first, form the folds, which are 
observed every where in the cavity of this 
viscus, and more particularly about the pylo- 
rus ; where they seem to impede the too has- 
ty exclusion of the aliment, making a conside- 
rable plait, called valvula pylori. 

The inner coat is constantly moistened by a 
mucus, which approaches to the nature of the 
saliva, and is called the gastric juice ; this li- 
quor has been supposed to be secreted by cer- 
tain minute glands* seated in the nervous tu- 
nic, whose excretory ducts open on the sur- 
face of the villous coat. 

The arteries of the stomach called the gas- 
tric arteries are principally derived from the 
caeliac ; some of its veins pass to the splenic, 
and others to the vena portae ; and its nerves 
are chiefly from the eighth pair or par vagum. 

* Heister, speaking of these glands, very properly says, M in 
porcis facile, in hom'im raro observantur ;" for although many 
anatomical writers have described their appearance and figure, 
yet they do not seem to have been hitherto satisfactorily demon- 
strated in the human stomach ; and the gastric juice is now more 
generally believed to be derived from the exhalent arteries of the 
stomach. 



Of the Abdomen. 243 

The account given of the tunics of the sto- 
mach may be applied to the whole alimentary 
canal ; for both the oesophagus and intestines 
are, like this viscus, composed of four coats. 

Before we describe the course of the ali- 
ment and the uses of the stomach, it will be 
necessary to speak of other parts which assist 
in the process of digestion. 

Sect. IV. Of the Oesophagus. 

The oesophagus or gullet is a membra- 
nous and muscular canal, extending from the 
bottom of the mouth to the upper orifice of 
the stomach. — Its upper part where the ali- 
ment is received is shaped somewhat like a 
funnel, and is called the pharynx. 

From hence it runs down close to the bo- 
dies of the vertebrae as far as the diaphragm, 
in which there is an opening through which ti 
passes, and then terminates in the stomach 
about the eleventh or twelfth vertebra of the 
back. 

The oesophagus is plentifully supplied with 
arteries from the external carotid, bronchial, 
and superior intercostal arteries.; its veins 
empty themselves into the vena azygos, inter- 
nal jugular, and mammary veins, he. 

Its nerves are derived chiefly from .the 
eighth pair. 

We likewise meet with a mucus in the oeso- 
phagus, which every where lubricates its in- 
ner surface, and tends to assist in deglutition. 
— This mucus seems to be secreted by very 
minute glands, like the mucus in other parts 
of the alimentary canal. 



244 Of the Abdomen. 



Sect. V. Of the Intestines. 

The intestines form a canal, which is usu- 
ally six times longer than the body to which 
it belongs- This canal extends from the py- 
lorus, or inferior orifice of the stomach, to the 
anus. 

It will be easily understood, that a part of 
such great length must necessarily make many 
circumvolutions, to be confined with so many 
other viscera within the cavity of the lower 
belly. 

Although the intestines are in fact, as we 
have observed, only one long and extensive 
canal, yet different parts have been distin- 
guished by different names. 

The intestines are first distinguished into 
two parts, one of which begins at the sto- 
mach, and is called the thin or small intestines, 
from the small size of the canal, when com- 
pared with the other part, which is called the 
large intestines, and includes the lower portion 
of the canal down to the anus. 

Each of these parts has its subdivisions. — 
The small intestines being distinguished into 
duodenum, jejunum, and ilium, and the larger 
portion into caecum, colon, and rectum. 

The small intestines fill the middle and fore 
parts of the belly, while the large intestines 
fill the sides and both the upper and lower 
parts of the cavity. 

The duodenum, which is the first of the 
small intestines, is so called, because it is 
about 12 inches long. It begins at the pylo- 



Of the Abdomen. 245 

rus and terminates in the jejunum, which is a 
part of the canal observed to be usually more 
empty than the ot >er intestines. — This appear- 
ance gives it its name, and likewise serves to 
point out where it begins. 

The next division is the ilium, which of it- 
self exceeds the united length of the duode- 
num and jejunum, and has received its name 
from its numerous circumvolutions. I he 
large circumvolution of the ilium covers the 
first of the large intestines called the ca'cutn,* 
which seems properly to belong to the colon, 
being a kind of pouch of about four fingers in 
width, and nearly of the same length, having 
exteriorly a little appendix, called appendix 
eaci. 

The caecum is placed in the cavity of the 
os ilium on the right side, and terminates in 
the colon, which is the largest of all the in- 
testines. 

This intestine ascends by the right kidney 
to which it is attached, passes under the hol- 
low part of the liver, and the bottom of the 
stomach, to the spleen, to which it is likewise 
secured, as it is also to the left kidney ; and 
from thence passes down towards the os sa- 
crum, where, from its straight course, the ca- 
nal begins to take the name of rectum. 

There are three ligamentous bands extend- 
ing through the whole length of the colon, 



* Anatomists have differed with respect to this division of the 
intestines. — The method here followed is now generally adopted ; 
but there are authors who allow the name of cacum only to the 
little appendix, which has likewise heen called the vermiform ap- 
pendix, from its resemblance to a worm in size and length. 



246 Of the Abdomen. 

which, by being shorter than its two inner 
coats, serve to increase the plaits on the in- 
ner surface of this gut. 

The anus which terminates the intestinum 
rectum, is furnished with three muscles ; one 
of these is composed of circular fibres, and 
from its use in shutting the passage of the 
anus is called sphincter ani. 

The other two are the levatores ani, so call- 
ed, because they elevate the anus after dejec- 
tion. When these by palsy, or any other dis- 
ease lose the power of contracting, the anus 
prolapses; and when the sphincter is affected 
by similar causes, the faeces are voided invo- 
luntarily. 

It has been already observed, that the in- 
testinal canal is composed of four tunics ; but 
it remains to be remarked, that here, as in 
the stomach, the two inner tunics being more 
extensive than the other two, form the plaits 
which are to be seen in the inner surface of 
the intestines, and are called valvule? conniven- 
tes. 

Some authors have considered these plaits 
as tending to retard the motion of the faeces, 
in order to afford more time for the separa- 
tion of the chyle ; but there are others who 
attribute to them a different use : they con- 
tend, that these valves, by being naturally in- 
clined downwards, cannot impede the descent 
of the fseces, but that they are intended to pre- 
vent their return upwards. 

They are probably destined for both these 
uses; for although these folds incline to their 
lower side, yet the inequalities they occasion 



Of the Abdomen. 247 

in the canal are sufficient to retard, in some 
measure, the progressive motion of the faeces, 
and to afford a greater surface for the absorp- 
tion of chyle, and their natural position seems 
to oppose itself to the return of the aliment. 

Besides these valvule conniventes, there is 
one more considerable than the rest, called the 
valve of the colon ; which is found at that part 
of the canal where the intestinum ilium is join- 
ed to the colon. This valve permits the ali- 
mentary pulp to pass downwards, but serves 
to prevent its return upwards ; and it is by 
this valve, that glysters are prevented from 
passing into the small intestines.* 

Of the little vermiform appendix of the cae- 
cum, it will be sufficient to say, that its uses 
have never yet been ascertained. In birds we 
meet with two of these appendices. 

The intestines are lubricated by a constant 
supply of mucus, which is probably secreted 
by very minute follicles. f This mucus pro- 
motes the descent of the alimentary pulp, and 
in some measure defends the inner surface of 



* This is not invariably the case, for the contents of a gly- 
stcr have been found not only to reach the small intestines, but 
to be voided at the mouth. Such instances, however, are not 
common. 

f Some writers have distinguished these glands into miliary, 
lenticular, &c. — Brunner and Peyer were the first anatomists 
who described the glands of the intestines, and their descrip- 
tions were chiefly taken from animals, these glandular appear- 
ances not seeming to have been hitherto satisfactorily pointed ouc 
in the human subject. — It is now pretty generally believed, that 
the mucus which every where lubricates the alimentary canal, is 
exhaled from the minute ends of arteries ; and that these ex- 
tremities first open into a hollow vesicle, from whence the depo- 
sited juice of several branches flows out through one commoi 
orifice. 



248 Of the Abdomen. 

the intestines from the irritation to which it 
would, perhaps, otherwise be continually ex- 
posed from tne aliment; and which, when in 
a certain degree, excites a painful disorder 
called colic, a name given to the disease, be- 
cause us most usual seat is in the intestinum 
colon. 

The intestines are likewise frequently dis- 
tended with air, and this distention sometimes 
occasions pain, and constitutes the flatulent 
colic. 

The arteries of the intestines are continu- 
ations of the mesenteric arteries, which are 
derived in two considerable branches from the 
aorta. — The redundant blood is carried back 
into the vena portarum. 

In the rectum the veins are called hemor- 
rhoidal, and are there distinguished into inter* 
nal and external : the first are branches of the 
inferior mesenteric vein, but the latter pass 
into other veins. Sometimes these veins are 
distended with blood from obstructions, from 
weakness of their coats, or from other causes, 
and what we call the hemorrhoids takes place. 
In this disease they are sometimes ruptured; 
and the discharge of blood which consequent- 
ly follows, has probably occasioned them to be 
called hemorrhoidal veins. 

The nerves of the intestines are derived 
from the eighth pair. 

Sect. VI. Of the Mesentery. 

The name of the mesentery implies its sim- 
ulation amidst the intestines. It is in fact a 



Of the Abdomen. 249 

part of the peritonaeum, being a reduplica- 
tion * of that membrane from each side of the 
lumbar vertebra.', to which it is firmly attach- 
ed, so that it is formed of two laminae, con- 
nected to each other by cellular membrane. 

The intestines, in their different circumvo- 
lutions, form a great number of arches, and 
the mesentery accompanies them through all 
these turns ; but by being attached only to the 
hollow part of each arch, it is found to have 
only a third of the extent of the intestines. 

That part of this membrane which accom- 
panies the small intestines is the mesentery, 
properly so called ; but those parts of it which 
are attached to the colon and rectum are dis- 
tinguished by the names of meso-colon and me- 
so-rectum. 

There are many conglobate glands dispers- 
ed through this double membrane, through 
which the lacteals and lymphatics pass in their 
way to the thoracic duct. The blood-vessels 
of the mesentery were described in speaking 
of the intestines. 

I i 

• He who only reads of the reduplication of membranes, 
will perhaps not easily understand how the periKnxum and 
pleura are reflected over the viscera in their several cavities ; 
for one of these serves the same purposes in the thorax that 
the other does in the abdomen. This disposition, for the dis- 
covery of which we are indebted to modern anatomists, con- 
stitutes a curious part of anatomical knowledge : but the stu- 
dent, unaided by experience, and assisted only by what the li- 
mits of this work would permit us to say on the occasion, would 
probably imbibe only confused ideas of the matter ; and it v-ill 
perfectly answer the present purpose, if he considers the me- 
sentei) as a membr.ine attached by one of its side;, to the lum- 
bar vertebrae, and by the other to the intestines. 



250 Of the Abdomen. 

This membrane, by its attachment to the 
vertebrae, serves to keep the intestines in their 
natural situation. The idea usually formed of 
the colic called miserere, is perfectly errone- 
ous ; it being impossible that the intestines 
can be twisted, as many suppose they are, in 
that disease, their attachment to the mesente- 
ry effectually preventing such an accident — 
but a disarrangement sometimes takes place 
in the intestinal canal itself, which is produc- 
tive of disagreeable and sometimes fatal con- 
sequences. — This is by an introsusception of 
the intestine, an idea of which may be easily 
formed, by taking the finger of a glove, and 
involving one part of it within the other. 

If inflammation takes place, the stricture in 
this case is increased, and the peristaltic mo- 
tion of the intestines (by which is meant the 
progressive motion of the faeces downwards) 
is inverted, and what is called the iliac passion 
takes place. The same effects may be occa- 
sioned by a descent of the intestine, or of the 
omentum either with it or by itself, and thus 
constituting what is called an hernial rupture ; 
a term by which in general is meant the falling 
down or protrusion of any part of the intes- 
tine or omentum, which ought naturally to be 
contained within the cavity of the belly. 

To convey an idea of the manner in which 
such a descent takes place, it will be necessa- 
ry to observe, that the lower edge of the ten- 
don of the musculus obliquus externus, is 
stretched from the fore-part of the os ilium 
or haunch-bone of the os pubis, and consti- 
tutes what is called PouparVs or Fallopius's lu 



Of the Abdomen. 251 

gament, forming an opening, through which 
pass the great crural artery and vein. Near 
the os pubis the same tendinous fibres are se- 
parated from each other, and form an opening 
on each side, called the abdominal ring, through 
which the spermatic vessels pass in men, and 
the ligamenta uteri in women. In consequence 
of violent efforts, or perhaps of natural causes, 
the intestines are found sometimes to pass 
through these openings ; but the peritonaeum 
which incloses them when in their natural ca- 
vity, still continues to surround them even in 
their descent. This membrane does not he- 
come torn or lacerated by the violence, as 
might be easily imagined ; but its dilatibility 
enables it to pass out with the viscus, which 
it incloses as it were in a bag, and thus forms 
what is called the hernial sac. 

If the hernia be under Poupart's ligament, 
it is called femoral; if in the groin, inguinal;* 
and scrotal, if in the scrotum- Different names 
are likewise given to the hernia as the con- 
tents of the sac differ, whether of omentum 
only or intestine, or both: — but these defini- 
tions more properly belong to the province of 
surgery. 

Sect. VII. Of the Pancreas* 

The pancreas is a conglomerate gland 
placed behind the bottom of the stomach, 
towards the first vertebra of the loins ; shaped 

* The hernia congenita will be considered with the male or- 
gans of generation, with which it is intimately connected. 



252 Of the Abdomen. 

like a dog's tongue, with its point stretched 
out towards the spleen, and its other end ex- 
tending towards the duodenum. It is about 
eight fingers breadth in length, two or three 
in width, and one in thickness. 

This viscus, which is of a yellowish colour, 
somewhat inclined to red, is covered with a 
membrane which it derives from the peritonae- 
um. Its arteries, which are rather numerous 
than large, are derived chiefly from the sple- 
nic and hepatic, and its veins pass into the 
veins of the same name. — Its nerves are de- 
rived from the intercostal. 

The many little glands of which it has been 
observed the pancreas is composed, all serve 
to secrete a liquor called the pancreatic juice, 
which in its colour, consistence, and other pro- 
perties, does not seem to differ from the sali- 
va. Each of these glands sends out a little 
excretory duct, which, uniting with others, 
help to form larger ducts ; and all these at last 
terminate in one common excretory duct (first 
discovered by Virtsungus in 1642), which 
runs through the middle of the gland, and is 
now usually called ductus pancreaticus Virt- 
sungi. This canal opens into the intestinum 
duodenum, sometimes by the same orifice with 
the biliary duct, and sometimes by a distinct 
opening. The liquor it discharges being of a 
mild and insipid nature, serves to dilute the 
alimentary pulp, and to incorporate it more 
easily with the bile. 



Of the Abdomen. 253 



Sect. VIII. Of the Liver. 

The liver is a viscus of considerable size, 
and of a reddish colour ; convex superiorly 
and anteriorly where it is placed under the 
ribs and diaphragm, and of an unequal sur- 
face posteriorly. It is chiefly situated in the 
right hypochondrium, and under the false ribs; 
but it likewise extends into the epigastric re- 
gion, where it borders upon the stomach. It 
is covered by a production of the peritonaeum, 
which serves to attach it by three of its redu- 
plications to the false ribs. These reduplica- 
tions are called ligaments, though very differ- 
ent in their texture from what are called by 
the same name in other parts of the body. The 
umbilical cord, too, which in the foetus is per- 
vious, gradually becomes a simple ligament 
after birth ; and, by passing to the liver, serves 
likewise to secure it in its situation. 

At the posterior part of this organ where 
the umbilical vessels enter, it is found divid- 
ed into two lobes. Of these, the largest is 
placed in the right hypochondrium ; the other, 
which covers part of the stomach, is called 
the little lobe. All the vessels which go to the 
liver pass in at the fissure we have mention- 
ed ; and the production of the peritoneum, 
which invests the liver, was described by Ghs- 
son, an English anatomist, as accompanying 
them in their passage, and surrounding them 
like a glove ; hence this production has been 
commonly known by the name of capsula of 
Glisson : but it appears to be chiefly a continu- 



254 Of the Abdomen. 

ation of the cellular membrane which covers 
the vena portae ventralis. 

The liver was considered by the ancients as 
an organ destined to prepare and perfect the 
blood ; but later discoveries have proved, that 
this opinion was wrong, and that the liver is a 
glandular substance formed for the secretion 
of the bile. 

The blood is conveyed to the liver by the 
hepatic artery and the vena porta?. This is 
contrary to the mode of circulation in other 
parts, where veins only serve to carry off the 
redundant blood : but in this viscus the hepa- 
tic artery, which is derived from the cseliac, is 
principally destined for its nourishment ; and 
t&e vena portae, which is formed by the union 
of the veins from most of the abdominal vis- 
cera, furnishes the blood from which the bile 
is chiefly to be separated ; so that these two 
series of vessels serve very distinct purposes. 
The vena portae, as it is ramified through the 
liver, performs the office both of a vein and 
an artery ; for like the former it returns the 
blood from the extremities of arteries, while 
as the latter it prepares it for secretion. 

The nerves of the liver are branches of the 
intercostal and par vagum. The bile, after be- 
ing separated from the mass of blood, in a 
manner of which mention will be made in 
another place, is conveyed out of this organ 
by very minute excretory ducts, called poribi- 
liarii ; these uniting together like the excreto- 
ry ducts in the pancreas, gradually form larger 
ones, which at length terminate in a considera- 
ble canal called ductus hepaticus. 



Of the Abdomen. 255 



Sect. IX. Of the Gall-bladder. 

The gall-blaclder is a little membranous, 
bag, shaped like a pear, and attached to the 
posterior and almost inferior part of the great 
lobe of the liver. 

It has two tunics; of which the exterior 
one is a production of the peritonaeum. The 
interior, or villous coat, is supplied with a mu- 
cus that defends it from the acrimony of the 
bile. These two coverings are intimately con- 
nected by means of cellular membrane, which 
from its firm glistening appearance has gene- 
rally been spoken of as a muscular tunic. 

The gall-bladder is supplied with blood- 
vessels from the hepatic arteries. These 
branches are called the cystic arteries , and 
the cystic veins carry back the blood. 

Its nerves are derived from the same origin 
as those of the liver. 

• The neck of the gall-bladder is continued 
in the form of a canal called ductus cysticus^. 
which soon unites with the ductus hepaticus- 
we described as the excretory duct of the li- 
ver ; and forming one common canal, takes the 
name of ductus coledochus communis, through 
which both the cystic and hepatic bile are dis- 
charged into the duodenum. This canal opens 
into the intestine in an oblique direction, first 
passing through the exterior tunic, and then 
piercing the other coats after running between 
each of them a very little way. This cecono- 
my serves two useful purposes ; — to promote 
the discharge of bile and to prevent its return. 



256 Of the Abdomen. 

The bile may be defined to be a natural li- 
quid soap, somewhat unctuous and bitter, and 
of a yellowish colour, which easily mixes with 
water, oil, and vinous spirits, and is capable 
of dissolving resinous substances. From some 
late experiments made by M. Cadet,* it ap- 
pears to be formed of an animal oil, combined 
with the alkaline base of sea-salt, a salt of the 
nature of milk, and a calcareous earth which 
is slightly ferruginous. 

Its definition seems sufficiently to point out 
the uses for which it is intended.t It blends 
the alimentary mass, by dividing and attenu- 
ating it ; corrects the too great disposition to 
acescency, which the aliment acquires in the 
stomach; and finally, by its acrimony, tends 
to excite the peristaltic motion of the intes- 
tines. 

After what has been said, it will be conceiv- 
ed that there are two sorts of bile ; one of 
which is derived immediately from the liver 
through the hepatic duct, and the other from 
the gall-bladder. These two biles, however, 
do not essentially differ from each other. The 
hepatic bile indeed is milder, and more liquid 
than the cystic, which is constantly thicker 
and yellower ; and by being bitterer, seems to 
possess greater activity than the other. 

Every body knows the source of the hepatic 
bile, that it is secreted from the mass of blood 
by the liver ; but the origin of the cystic bile 

* Mem. de V Acad, des Sciences, 1767. 

f The ancients, who were not acquainted with the real use 
of the liver, considered the bile as an excrementiLicus and use- 
less fluid. 



Of the Abdomen. 257 

has occasioned no little controversy amongst 
anatomical writers. There are some who con- 
tend, that it is separated in the substance of 
the liver, from whence it passes into the gall- 
bladder through particular vessels. In deer, 
and in some other quadrupeds, as well as in 
several birds and fishes, there is an evident 
communication, by means of particular ves- 
sels, between the liver and the gall-bladder. 
Bianchi, Winslow, and others, have asserted 
the existence of such vessels in the human 
subject, and named them hepaticystic ducts ; 
but it is certain that no such ducts exist. — In 
obstructions of the cystic duct, the gall-blad- 
der has been found shrivelled and empty: so 
that we may consider the gall-bladder as a reser- 
voir of hepatic bile ; and that it is an establish- 
ed fact that the whole of the bile contained in 
the gall-bladder is derived from the liver ; that 
it passes from the hepatic to the cystic duct, 
and from that to the gall-bladder. The differ- 
ence in the colour, consistence, and taste of 
the bile, is merely the consequence of stagna- 
tion and absorption. When the stomach is 
distended with aliment, this reservoir under- 
goes a certain degree of compression, and the 
bile passes out into the intestinal canal ; and 
in the efforts to vomit, the gall-bladder seems 
to be constantly affected, and at such times dis- 
charges itself of its contents. 

Sometimes the bile concretes in the gall- 
bladder, so as to form what are called gall- 

K k 



258 Of the Abdomen. 

stones.* When these concretions pass into 
the cystic duct, they sometimes occasion ex- 
quisite pain, by distending the canal in their 
way to the duodenum ; and by lodging in the 
ductus choledochus communis, and obstruct- 
ing the course of the bile, this fluid will be 
absorbed, and by being carried back into the 
circulation occasion a temporary jaundice. 

Sect. X. Of the Spleen. 

The spleen is a soft and spongy viscus, of 
a bluish colour, and about five or six fingers 
breadth in length, and three in width, situated 
in the left hypochondrium, between the sto- 
mach and the false ribs. That side of it which 
is placed on the side of the ribs is convex ; and 
the other, which is turned toward the stomach, 
is concave. 

The splenic artery, which is a branch from 
the caeliac, supplies this viscus with blood, and 
a vein of the same name carries it back into 
the vena portae. 

Its nerves are derived from a particular 
plexus called the splenic, which is formed by 
branches of the intercostal nerve, and by the 
eighth pair, or par vagum. 

The ancients, who supposed two sorts of 
bile, considered the spleen as the receptacle 
of what they called atra bilis. Havers, who 

* These concretions sometimes remain in the gall-bladder 
without causing any uneasiness. Dr. Heberden relates, that a 
gall-stone weighing two drams was found in the gall-bladder of 
the late Lord Bath, though he had never complained of the 
jaundice, nor of any disorder which he could attribute to that 
cause. Med. Trans. Vol. ii. 



Of the Abdomen. 259 

wrote professedly on the bones, determined its 
use to be that of secreting the synovia ; and 
the late Mr. Hewson imagined, that it concur- 
red with the thymus and lymphatic glands of 
the body in forming the red globules of the 
blood. All these opinions seem to be equally 
fanciful. The want of an excretory duct has 
occasioned the real use of this viscus to be 
still doubtful. Perhaps the blood undergoes 
some change in it, which may assist in the pre- 
paration of the bile. This is the opinion of 
the generality of modern physiologists ; and 
the great quantity of blood with which it is 
supplied, together with the course of its veins 
into the vena portse, seem to render this no- 
tion probable. 

Sect. XI. Of the Glandulce Renales, Kidneys, 
and Ureters, 

The glandulse renales, which were by the 
ancients supposed to secrete the atra bilis, and 
by them named capsulte atrabilares, are two 
flat bodies of an irregular figure, one on each 
side between the kidney and the aorta. 

In the foetus they are as large as the kidneys : 
but they do not increase afterwards in propor- 
tion to those parts ; and in adults and old peo- 
ple they are generally found shrivelled, and 
much wasted. They have their arteries and 
veins. Their arteries usually arise from the 
splenic or the emulgent, and sometimes from 
the aorta ; and their veins go to the neighbour- 
ing veins, or to the vena cava. Their nerves 
are branches of the intercostal 



260 Of the Abdomen. 

The use of these parts is not yet perfectly- 
known. In the foetus the secretion of urine 
must be in a very small quantity, and a part 
of the blood may perhaps then pass through 
these channels, which in the adult is carried to 
the kidneys to supply the matter of urine. 

The kidneys are two in number, situated 
one on the right and the other on the left side 
in the lumbar region, between the last false 
rib and the os ilium, by the sides of the verte- 
brae. Each kidney in its figure resembles a 
sort of bean, which from its shape is called 
kidney-bean. The concave part of each kidney 
is turned towards the aorta and vena cava as- 
cendens. They are surrounded by a good 
deal of fat, and receive a coat from the peri- 
tonaeum ; and when this is removed, a very 
fine membrane is found investing their sub- 
stance and the vessels which ramify through 
them. 

Each kidney has a considerable artery and 
vein, which are called the emulgent. The ar- 
tery is a branch from the aorta, and the vein 
passes into the vena cava. Their nerves, 
which every where accompany the blood- 
vessels, arise from a considerable plexus, 
which is derived from the intercostal. 

In each kidney, which in the adult is of a 
pretty firm texture, there are three substances 
to be distinguished.* The outer part is glan- 
dular or cortical, beyond this is the vascular 

* The kidneys in the foetus are distinctly lobulated ; but in 
the adult they become perfectly firm, smooth, and regular. 



Of the Abdomen. 261 

or tubular substance, and the inner part is pa- 
pillary or membranous. 

It is in the cortical part of the kidney that 
the secretion is carried on ; the urine being 
here received from the minute extremities of 
the capillary arteries, is conveyed out of this 
cortical substance by an infinite number of ve- 
ry small cylindrical canals or excretory ves- 
sels, which constitute the tubular part. These 
tubes, as they approach the inner substance 
of the kidney gradually unite together ; and 
thus forming larger canals, at length termi- 
nate in ten or twelve little protuberances call- 
ed papilla, the orifices of which may be seen 
without the assistance of glasses. These pa- 
pillae open into a small cavity or reservoir 
called the pelvis of the kidney, and formed by 
a distinct membranous bag which embraces 
the papillae. From this pelvis the urine is 
conveyed through a membranous canal which 
passes out from the hollow side of the kidney, 
a little below the blood-vessels, and is called 
ureter. 

The ureters are each about as large as a 
common writing-pen. They are somewhat 
curved in their course from the kidneys, like 
the letter^ and at length terminate in the pos- 
terior and almost inferior part of the bladder, 
at some distance from each other. They pass 
into the bladder in the same manner as the 
ductus choledochus communis passes into the 
intestinum duodenum, not by a direct passage, 
but by an oblique course between the two 
coats ; so that the discharge of urine into the 
bladder is promoted, whilst its return is pre- 



262 Of the Abdomen. 

vented. Nor does this mode of structure pre- 
vent the passage of fluids only from the blad- 
der into the ureters, but likewise air : — for air 
thrown into the bladder inflates it, and it con- 
tinues to be distended if a ligature is passed 
round its neck ; which seems to prove suffici- 
ently that it cannot pass into the ureters. 

Sect. XII. Of the Urinary Bladder. 

The urinary bladder is a membranous and 
muscular bag of an oblong roundish shape, 
situated in the pelvis, between the os pubis 
and intestinum rectum in men, and between 
the os pubis and uterus in women. Its up- 
per and widest part is usually called the bot- 
tom, its narrow part the neck of the bladder ; 
the former only is covered by the peritonaeum. 

The bladder is formed of three coats, con- 
nected together by means of cellular mem- 
brane. The external or peritonseal, is only a 
partial one, covering the upper and back part 
of the bladder. The middle, or muscular 
coat, is composed of irritable, and of course 
muscular fibres, which are most collected 
around the neck of the bladder, but not so 
as to form a distinct muscle, or sphincter, as 
the generality of anatomists have hitherto sup- 
posed. 

The inner coat, though much smoother, has 
been said to resemble the villous tunic of the 
intestines, and like that is provided with a 
mucus, which defends it against the acrimony 
of the urine. 



Of the Abdomen. 263 

It will be easily conceived from what has 
been said, that the kidneys are two glandular 
bodies, through which a saline and excremen- 
titious fluid called urine is constantly filtering 
from the mass of blood. 

While only a small quantity of urine is col- 
lected in the bladder, it excites no kind of un- 
easiness ; but when a greater quantity is ac- 
cumulated, so that the bladder is distended in 
a certain degree, it excites in us a certain sen- 
sation, which brings on as it were a voluntary 
contraction of the bladder to promote its dis- 
charge. — But this contraction is not effected 
by the muscular fibres of the bladder alone : 
for all the abdominal muscles contract in obe- 
dience to our will, and press downwards all 
the viscera of the lower belly ; and these pow- 
ers being united, at length overcome the re- 
sistance of the fibres surrounding the neck of 
the bladder, which dilates and affords a pas- 
sage to the urine through the urethra. 

The frequency of this evacuation depends 
on the quantity of urine secreted ; on the de- 
gree of acrimony it possesses ; on the size of 
the bladder, and on its degree of sensibility. 

The urine varies much in its colour and 
contents. These varieties depend, on age, sex. 
climate, diet, and other circumstances. In in- 
fants it is generally a clear watery fluid, with- 
out smell or taste. As we advance in life, it 
acquires more colour and smell, and becomes 
more impregnated with salts. In old people 
it becomes still more acrid and fetid. 

In a healthy state it is nearly of a straw co- 
lour. — After being kept for some time, it de- 



264 Of the Abdomen, 

posites a tartarous matter, which is found 
to be composed chiefly of earth and salt, and 
soon incrusts the sides of the vessel in which 
it is contained. While this separation is tak- 
ing place, appearances like minute fibres or 
threads of a whitish colour may be seen in the 
middle of the urine, and an oily scum observ- 
ed floating on its surface. So that the most 
common appearances of the urine are suffici- 
ent to ascertain that it is a watery substance, 
impregnated with earthy, saline, and oily par- 
ticles. 

The urine is not always voided of the same 
colour and consistence: for these are found to 
depend on the proportion of its watery part to 
that of its other constituent principles. — Its co- 
lour and degree of iluidity seem to depend on 
the quantity of saline and inflammable parti- 
cles contained in it: so that an increased pro- 
portion of those parts will constantly give the 
urine a higher colour, and add to the quanti- 
ty of sediment. 

The variety in the appearance of the urine, 
depends on the nature and quantity of solid 
and fluid aliment we take in ; and it is like- 
wise occasioned by the different state of the 
urinary vessels, by which we mean the chan- 
nels through which it is separated from the 
blood, and conveyed through the pelvis into 
the ureters. The causes of calculous concre- 
tions in the urinary passages, are to be looked 
for in the natural constitution of the body, 
mode of life, &c. 

It having been observed, that after drink- 
ing any light wine or Spa water, it very soon 



Of the Abdomen. 265 

passed off by urine, it has been supposed by 
some, that the urine is not altogether convey- 
ed to the bladder by the ordinary course of 
circulation, but that there must certainly exist 
some other shorter means of communication, 
perhaps by certain vessels between the sto- 
mach and the bladder, or by a retrograde motion 
in the lymphatics. But it is certain, that if we 
open the belly of a dog, press out the urine 
from the bladder, pass a ligature round the 
emulgent arteries, and then sew up the abdo- 
men, and give him even the most diuretic li- 
quor to drink, the stomach and other chan- 
nels will be distended with it, but not a drop 
of urine will be found to have passed into the 
bladder ; or the same thing happens when a 
ligature is thrown round the two ureters. This 
experiment then seems to be a sufficient proof, 
that all the urine we evacuate, is conveyed to 
the kidneys through the emulgent arteries, in 
the manner we have described. — It is true, that 
wine and other liquors promote a speedy eva- 
cuation of urine : but the discharge seems tx> 
be merely the effect of the stimulus they occa- 
sion ; by which the bladder and urinary parts 
are solicited to a more copious discharge of the 
urine, which was before in the body, and not 
immediately of that which was last drank ; and 
this increased discharge, if the supply is kept 
up, will continue : nor will this appear won- 
derful, if we consider the great capacity of the 
vessels that go to the kidneys ; the constant sup- 
ply of fresh blood that is essential to health ; 
and the rapidity with which it is incessantly 

L J 



266 Of the Abdomen. 

circulated through the heart to all parts of the 
body. 

Sect. XIII. Of Digestion. 

We are now proceeding to speak of diges- 
tion, which seems to be introduced in this 
place with propriety, after a description of the 
abdominal viscera, the greater part of which 
contribute to this function. By digestion is to 
be understood, the changes the aliment under- 
goes for the formation of chyle : — these chan- 
ges are effected in the mouth, stomach, and 
small intestines. 

The mouth, of which every body has a ge- 
neral knowledge, is the cavity between the 
two jaws, formed anteriorly and laterally by 
the lips, teeth, and cheeks, and terminating 
posteriorly in the throat. 

The lips and cheeks are made up of fat and 
muscles, covered by the cuticle, which is con- 
tinued over the whole inner surface of the 
mouth, like a fine and delicate membrane. — 
Besides this membrane, the inside of the mouth 
is furnished with a spongy and very vascular 
substance called the gums, by means of which 
the teeth are secured in their sockets. A simi- 
lar substance covers the roof of the mouth, 
and forms what is called the velum pendulum 
palati, which is fixed to the extremity of the 
arch formed by the ossamaxillaria andossa pa- 
lati, and terminates in a soft, small, and coni- 
cal body, named uvula; which appears, as it 
were, suspended from the middle of the arch 
over the basis of the tongue. 



Of the Abdomen. 267 

The velum pendulum palati performs the 
office of a valve between the cavity of the 
mouth and the pharynx, being moved by se- 
veral muscles.* 

The tongue is composed of several mus- 
clesf which enable it to perform a variety of 
motions for the articulation of the voice ; for 
the purposes of mastication ; and for convey- 
ing the aliment into the pharynx. Its upper 
part is covered with papillae, which constitute 
the organ of taste, and are easily to be dis- 
tinguished ; it is covered by the same mem- 
brane that lines the inside of the mouth, an$ 
which makes at its inferior part towards its ba- 
sis a reduplication called frtenum. 

Posteriorly, under the velum palati, and at 
the basis of the tongue, is the pharynx : which 
is the beginning of the oesophagus, stretched 
out everyway, so as to resemble the top of a 
funnel, through which the aliment passes into 
the stomach. 

The mouth has a communication with the 
nostrils at its posterior and upper part: with 
the ears, by the Eustachian tubes ; with the 
lungs, by means of the larynx ; and with the 
stomach, by means of the oesophagus. 

The pharynx is constantly moistened by a 
fluid, secreted by two considerable glands call- 
ed the tonsils, one on each side of the velum 
palati. These glands, from their supposed re- 

* These are the circumflexus palati, levator palati mollis, pa- 
lato-pharyngceus, constrictor isthmi faucium and azygos uvulae. 
See pages 191, 192, 193. 

f These are, the genio-glossus, hyo-glossus, lingualis, and 
stylo-glossus. See page 191. 



268 Of the Abdomen. 

.semblance to almonds, have likewise been call- 
ed amygdalus. 

The mouth is moistened by a considerable 
quantity of saliva. This fluid is derived from 
the parotid glands ; a name which by its ety- 
mology points out their situation to be near the 
cars. They are two in number, one on each 
side under the os mala? : and they are of the 
conglomerate kind ; being formed of many 
smaller glands, each of which sends out a very 
small excretory duct, which unites with the 
rest, to form one common channel, that runs 
Over the cheek, and piercing the buccinator 
muscle, opens into the mouth on each side, by 
an orifice into which a bristle may be easily in- 
troduced. — Besides these, the maxillary glands, 
which are placed near the inner surface of the 
angle of the lower jaw on each side ; the sub- 
lingual glands, which are situated at the root 
of the tongue ; the glands of the palate, which 
are seated in the velum palati ; and those of 
the cheeks, lips, &e. together with many other 
less considerable ones, — pour the saliva into 
the mouth through their several excretory 
ducts. 

The saliva, like all the other humors of the 
body, is found to be different in different peo- 
ple : but in general, it is a limpid and insipid 
fluid, without smell in healthy subjects; and 
these properties would seem to prove that it 
contains very few saline or inflammable parti- 
cles. 

The uses of the saliva seem to be to moisten 
and lubricate the mouth, and to assist in re- 



Of the Abdomen. 269 

during the aliment into a soft pulp before it is 
conveyed into the stomach. 

The variety of functions which are constant- 
ly performed by the living body, must neces- 
sarily occasion a continual waste and dissipa- 
tion of its several parts. A great quantity is 
every day thrown off by the insensible perspi- 
ration and other discharges ; and were not these 
losses constantly recruited by a fresh supply of 
chyle, the body would soon effect its own dis- 
solution. But nature has very wisely favour- 
ed us with organs fitted to produce such a sup- 
ply ; and has at the same time endued us with 
the sensations of hunger and thirst, that our 
attention may not be diverted from the neces- 
sary business of nutrition- The sensation of 
hunger is universally known ; but it would 
perhaps be difficult to describe it perfectly in 
words. It may, however, be defined to be a 
certain uneasy sensation in the stomach, which 
induces us to wish for solid food; and which 
likewise serves to point out the proper quan- 
tity, and time for taking it. In describing the 
stomach, mention was made of the gastric juice, 
as every where lubricating its inner coat. This 
humor mixes itself with the aliment in the sto-* 
mach, and helps to prepare it for its passage 
into the intestines \ but when the stomach is 
perfectly empty, this same fluid irritates the 
coats of the stomach itself, and produces the 
sensation of hunger. 

A certain proportion of liquid aliment is re- 
quired to assist in the process of digestion, and 
to afford that moisture to the body, of which 
there is such a constant dissipation. — Thirst 
induces us to take this necessary supply of 



i>70 Of the Abdomen. 

drink ; and the seat of this sensation is in the 
tongue, fauces, and oesophagus, which from 
their great sensibility are required to be kept 
moist : for though the fauces are naturally 
moistened by the mucus and salival juices; 
yet the blood, when deprived of its watery 
part or rendered acrimonious by any natural 
causes, never fails particularly to affect these 
parts, and the whole alimentary canal, and to 
occasion thirst. — This is the common effect 
of fevers and of hard labour, by both which too 
much of the watery part of the blood is dis- 
sipated, 

It has been observed, that the aliment un- 
dergoes some preparation in the mouth before 
it passes into the stomach ; and this prepara- 
tion is the effect of mastication. In treating of 
the upper and lower jaws, mention was made of 
the number and arrangement of the teeth. The 
upper jaw was described as being immoveable ; 
but the lower jaw was spoken of as being capable 
of elevation and depression, and of a grinding 
motion. The aliment, when first carried into 
the mouth, is pressed between the teeth of the 
two jaws by a very strong and frequent motion 
of the lower jaw; and the tongue and the cheeks 
assisting in this process, continue to replace the 
food between the teeth till it is perfectly divid- 
ed, and reduced to the consistence of pulp. 
The incisores and canini divide it first into 
smaller pieces, but it is between the surfaces of 
the dentes molares by the grinding motion of 
the jaw that the mastication is completed. 

During this process the salival glands being 
gently compressed by the contraction of the 



Of the Abdomen. 27 i 

muscles that move the lower jaw, pour out their 
saliva: this helps to divide and break down 
the food, which at length becomes a kind of pulp, 
and is then carried over the basis of the tongue 
into the fauces. But to effect this passage into 
the oesophagus, it is necessary that the other 
openings which were mentioned as having a 
communication with the mouth as well as the 
pharynx, should be closed ; that none of the 
aliment, whether solid or liquid T may pass into 
them, whilst the pharynx alone is dilated to re- 
ceive it : — And such a disposition actually takes 
place in a manner we will endeavour to de- 
scribe. 

The trachea arteria, or windpipe, through 
which the air is conveyed to the lungs, is plac- 
ed before the oesophagus — in the act of swat- 
lowing; therefore, if the larynx (for so the up- 
per part of the trachea is called) is not closed, 
the aliment will pass into it in its way to the 
oesophagus. But this is prevented by a small 
and very elastic cartilage, called epiglottis, which 
is attached only to the fore-part of the larynx ; 
so that the food in its passage to the oesopha- 
gus presses down this cartilage, which then co- 
vers the glottis or opening of the larynx ; and 
at the same time the velum palati being capable 
of some degree of motion, is drawn backwards 
by its muscles, and closes the openings into the 
nose and the Eustachian tubes. — This, howe- 
ver, is not all. The larynx, which being com- 
posed of cartilaginous rings, cannot fail in its 
ordinary state to compress the membranous ca- 
nal of the oesophagus, is in the act of degluti- 
tion carried forwards and upwards by muscles 



27.2 Of the Abdomen, 

destined for that purpose ; and consequently 
drawing the fore-part of the pharynx with it, 
that opening is fully dilated. When the ali- 
ment has reached the pharynx, its descent is 
promoted by its own proper weight, and by the 
muscular fibres of the oesophagus, which con- 
tinue to contract from above downwards, until 
the aliment has reached the stomach. That 
these fibres have no inconsiderable share in de- 
glutition, any person may experience, by 
swallowing with his head downwards, when the 
descent of the aliment cannot possibly be ef- 
fected by its weight. 

It is necessary that the nostrils and the lungs 
should communicate with the mouth, for the 
purposes of speech and respiration: but if the 
most minute part of our food happens to be 
introduced into the trachea, it never fails to 
produce a violent cough, and sometimes the 
most alarming symptoms. This is liable to 
happen when we laugh or speak in the act of 
deglutition : the food is then said to have passed 
the wrong way. And indeed this is not im- 
properly expressed: for death would soon fol- 
low, if the quantity of aliment introduced into 
the trachea should be sufficient to obstruct the 
respiration only during a very short time ; or 
if the irritating particles of food should not 
soon be thrown up again by means of the 
cough, which in these cases very seasonably 
increases in proportion to the degree of irrita- 
tion. 

If the velum palati did not close the passage 
to the nostrils, deglutition would be performed 
with difficulty, and perhaps not at all ; for the 



Of the Abdomen. 273 

aliment would return through the nose, as is 
sometimes the case in drinking. Children, 
from a deficiency in this velum palati, have 
been seen to die a few hours after birth ; and 
they who from disease or any other causes 
have not this part perfect, swallow with diffi- 
culty. 

The aliment, after having been sufficiently 
divided by the action of the teeth, and attenu- 
ated by the saliva, is received into the stomach, 
where it is destined to undergo a more consi- 
derable change. 

The properties of the aliment not being much 
altered at its first entrance into the stomach, 
and before it is thoroughly blended with the 
gastric juice, is capable of irritating the inner 
coat of the stomach to a certain degree, and 
occasions a contraction of its two orifices. — In 
this membranous bag, surrounded by the abdo- 
minal viscera, and with a certain degree of na- 
tural heat, the aliment undergoes a constant 
agitation by means of the abdominal muscles 
and of the diaphragm, and likewise by a cer- 
tain contraction or expansion of the muscular 
fibres of the stomach itself. By this motion, 
every part of the food is exposed to the action 
of the gastric juice, which gradually divides 
and attenuates it, and prepares it for its pas- 
sage into the intestines. 

Some observations lately published by Mr. 
Hunter in the Philosophical Transactions, tend 
to throw considerable light on the principles of 
digestion. There are few dead bodies in which 
the stomach, at its great end, is not found to, 

M m 



274 " Of the Abdomen. 

be in some degree digested *. Animals, or 
parts of animals, possessed of the living prin- 
ciple, when taken into the stomach, are not in 
the least affected by the action of that viscus ; 
but the moment they lose the living principle, 
they become subject to its digestive powers. 
This seems to be the case with the stomach, 
which is enabled to resist the action of its juices 
in the living body : but when deprived of the 
living principle, it is then no longer able to resist 
the powers of that menstruum, which it had it- 
self formed for the digestion of its contents; 
the process of digestion appearing to be conti- 
nued after death. This is confirmed by what 
happens in the stomachs of fishes : they fre- 
quently swallow, without mastication, fish 
which are larger than the digesting parts of their 
stomach can contain ; and in such cases, that 
part which is taken into the stomach is more 



* The Abbe Spallanzani, who has lately written upon di- 
gestion, finds, from a variety of experiments, made upon quadru- 
peds, birds, and fishes, that digestion goes on for some time after 
death, though far less considerable than in living animals ; but 
heat is necessary in many animals, or at least promotes it in a 
much greater degree. He found also, that when the stomach 
was cut out of the body, it had somewhat of the power of diges- 
tion, though this was trifling when compared with that which 
took place when the stomach was left in the body. In not one 
of the animals was the great curvature of the stomach dissolved, 
or much eroded after death. There was often a little erosion, 
especially in different fishes ; in which, when he had cleared the 
stomach of its contents, the internal coat was wanting. In other 
animals there was only a slight excoriation ; and the injury in all 
of them was at the inferior part, or great curvature. The coats 
of the stomach suffer less after death than flesh, or part of the 
stomach of similar animals put into it : the author assigns as a 
reason for this, that these bodies are invested on all sides by the 
gastric fluid, whereas it only acts on the internal surface of the 
stomach. 



Of the Abdomen. 275 

or less dissolved, while that part which re- 
mains in the oesophagus is perfectly sound ; 
and here, as well as in the human body, the 
digesting part of the stomach is often reduced 
to the same state as the digested part of the 
food. These appearances tend to prove, that 
digestion is not effected by a mechanical power, 
by contractions of the stomach, or by heat ; 
but by a fluid secreted in the goats of the sto- 
mach, which is poured into its cavity, and 
there animalizes the food, or assimilates it to 
the nature of blood. 

From some late experiments by M. Sage, * 
it appears, that inflammable air has the proper- 
ty of destroying and dissolving the animal tex- 
ture : and as we swallow with the substances 
which serve us for food a great quantity of at- 
mospherical air, 1VL Sage thinks it possible, 
that dephlogisticated, which is its principle, 
may be converted in the stomach into inflam- 
mable air, or may modify into inflammable air 
a portion of the oily substance which is 
the principle of aliments. In this case, would 
not the inflammable air (he asks), by dissolv- 
ing our food, facilitate its conversion into 
chyle ? 

Be this as it may, the food after having re- 
mained one, two, or three hours in the stomach, 
is converted into a greyish pulp, which is usu- 
ally called chymusy a word of Greek etymolo- 
gy, signifying juice, and some few milky or 
chylous particles begin to appear. — But the 

* Hist, de l'Academie royale des Sciences, &c. ppur 1784* 
mem. 15. 



276 Of the Abdomen. 

term of its residence in this bag is proportion- 
ed to the nature of the aliment, and to the state 
of the stomach and its juices. The thinner and 
more perfectly digested parts of the food pass 
by a little at a time into the duodenum, through 
the pylorus, the fibres of which relax to afford 
it a passage ; and the grosser and less digested 
particles remain in the stomach, till they ac- 
quire a sufficient fluidity to pass into the intes- 
tines, where the nature of the chymus is per- 
fectly changed. The bile and pancreatic juice 
which flow into the duodenum, and the mucus, 
which is every where distilled from the surface 
of the intestines, mix themselves with the ali- 
mentary pulp, which they still farther attenu- 
ate and dissolve, and into which they seem to 
infuse new properties. 

Two matters very different from each other 
in their nature and destination, are the result 
of this combination. — One of these, which is 
composed of the liquid parts of the aliment, 
and of some of its more solid particles, ex- 
tremely divided and mixed with the juices we 
have described, constitutes a very mild, sweet, 
and whitish fluid, resembling milk, and distin- 
guished by the name of chyle. This fluid is ab- 
sorbed by the lacteal veins, which convey it in- 
to the circulation, where, by being assimilated 
into the nature of blood, it affords that supply 
of nutrition, which the continual waste of the 
body is found to require. — The other is the re- 
mains of the alimentary mass deprived of all 
its nutritious particles, and containing only 
such parts as were rejected by the absorbing 
mouths of the lacteals. This grosser part, 



Of the Abdomen. 277 

called the feces, passes on through the course 
of the intestines, to be voided at the anus, 
as will be explained hereafter ; for this process 
in the ceconomy cannot be well understood till 
the motion of respiration has been explained. 
But the structure of the intestines is a subject 
which may be properly described in this place, 
and deserves to be attended to. 

It has been already observed, that the intes- 
tinal canal is five or six times as long as the bo- 
dy, and that it forms many circumvolutions in 
the cavity of the abdomen, which it traverses 
from the right to the left, and again from the 
left to the right ; in one place descending, and 
in another extending itself upwards. It was 
noticed likewise, that the inner coat of the in- 
testines, by being more capacious than their ex- 
terior tunics, formed a multitude of plates plac- 
ed at a certain distance from each other, and 
called valvule conniventes. Now this disposi- 
tion will be found to afford a farther proof of 
that divine wisdom, which the anatomist and 
physiologist cannot fail to discover in all their 
pursuits. — For if the intestinal canal was much 
shorter than it naturally is ; if instead of the 
present circumvolutions it passed in a direct 
course from the stomach ; and if its inner sur- 
face was smooth and destitute of valves ; the 
aliment would consequently pass with great ra- 
pidity to the anus, and sufficient time would be 
wanting to assimilate the chyle, and for the ne- 
cessary absorption of it into the lacteals : so 
that the body would be deprived of the supply 
of nutrition, which is so essential to life and 
health ; but the length and circumvolutions of 



278 Of the Abdomen. 

the intestines, the inequality of their internal 
surface, and the course of the aliment through 
them, all concur to perfect the separation of 
the chyle from the fasces, and to afford the ne- 
cessary nourishment to the body. 

Sect. XIV. Of the Course of the Chyle ', and 
of the Lymphatic System. 

An infinite number of very minute vessels, 
called the lacteal veins, arise like net-work from 
the inner surface of the intestines, (but princi- 
pally from the jejunum and ilium), which are 
distended to imbibe the nutritious fluid or 
chyle. These vessels, which were discovered 
by Asellius in 1622, * pass obliquely through 
the coats of the intestine, and running along 
the mesentery, unite as they advance, and form 
larger branches, all of which pass through the 
mesenteric or conglobate glands, which are ve- 
ry numerous in the human subject. As they 

* We are informed by Galen, that the lacteals had been seen 
in kids by Erasistratus, who considered them as arteries carrying 
a milky fluid : but from the remote time in which he lived, they 
do not seem to have been noticed till they were discovered in a 
living dog by Asellius, who denominated diem lacteahy and con- 
sidered them as serving to convey the chyle from the intestines to 
the liver ; for before the discovery of the thoracic duel:, the use 
of the liver was universally supposed to be that of converting the 
chyle into blood. But the discovery of the thoracic duct by Pec- 
quet, not long after, corrected this error. Pecquet very candidly 
confesses, that this discovery accidentally arose from his observ- 
ing a white fluid, mixed with the blood, flowing out of the vena 
cava, after he had cut off the heart of a living dog ; which he sus- 
pected to be chyle, and afterwards traced to its source from the 
thoracic duct : this duct had been seen near an hundred years be- 
fore in a horse by Eustachius, who speaks of it as a vein of a 
particular structure, but without knowing any thing of its termi- 
nation or use. 



Of the Abdomen. 279 

run between the intestines and these glands, 
they are styled vena? lactea? primi generis : but 
after leaving these glands, they are found to be 
less numerous, and being increased in size, are 
then called vena Iactea? secundi generis, which 
go to deposite their contents in the thoracic duct, 
through which the chyle is conveyed into the 
blood. 

This thoracic duct begins about the lower 
part of the first vertebra lumborum, from 
whence it passes up by the side of the aorta, 
between that and the vena azygos, close to the 
vertebra?, being covered by the pleura. Some- 
times it is found divided into two branches ; but 
they usually unite again into one canal, which 
opens into the left subclavian vein, afterhaving 
run a little way in an oblique course between 
its coats. The subclavian vein communicates 
with the vena cava, which passes to the right 
auricle of the heart. 

The lower part of this duct being usually larg- 
er than any other part of it, has been named 
receptaculum chyli, or Pecquet' 's receptacle in 
honour of the anatomist who first discovered 
it in 1651. In some quadrupeds, in turtle and 
in fish, this enlargement * is more considera- 
ble in proportion to the size of the duct, than it 
usually is in the human subject, where it is not 
commonly found large enough to merit the 
name of receptaculum. 

Opportunities of observing the lacteals in 
the human subject do not often occur; bin. 
they may be easily demonstrated in a dog Or 

* Hcwson's Exp. Inq. Part II. 



280 Of the Abdomen. 

any other quadruped that is killed two or three 
hours after feeding upon milk, for then they 
appear filled with white chyle. 

But these lacteals which we have described, as 
passing from the intestines through the mesen- 
tery to the thoracic duct, compose only a part 
of a system of vessels which perform the of- 
fice of absorption, and which constitute, with 
their common trunk the thoracic duct, and the 
conglobate glands that are dispersed through 
the body, what may be styled the lymphatic 
system. So that what is said of the structure 
of one of these series of vessels may very 
properly be applied to that of the other. 

The lymphatic veins* are minute pellucid 
tubes, which, like the lacteals, direct their 
course towards the centre of the body, where 
they pour a colourless fluid into the thoracic 
duct. The lymphatics from all the lower parts 
of the body gradually unite as they approach 
this duct, into which they enter by three or 
four very large trunks, that seem to form the 
lower extremity of this canal, or receptaculum 

* The arteries in their course through the body becoming gra- 
dually too minute to admit the red globules of the blood, have 
then been styled capillary or lymphatic arteries. The vessels which 
are here described as constituting the lymphatic system, were at 
first supposed to be continued from those arteries, and to convey 
back the lvmph, either into the red veins or the thoracic duct ; the 
office of absorption having been attributed to the red veins. But 
we know that the lymphatic veins are not continuations of the lym- 
phatic arteri?j,but that they constitute the absorbent system. There are 
still, however, some very respectable names among the anatomists 
of the present age, who contend, that the red veins act likewise 
as absorbents : — but it seems to have been clearly proved, that the 
red veins do absorb nowhere but in the cavernous cells of the 
penis, the erection of which is occasioned by a distention of those 
cells with arterial blood. 



Of the Abdomen. 281 

chyli, which may be considered as the great 
trunk of the lymphatic system. The lacteals 
open into it near the same place ; and the lym- 
phatics, from a large share of the upper parts 
of the body, pour their lymph into different 
parts of this duct as it runs upwards, to termi- 
nate in the left subclavian vein. The lympha- 
tics from the right side of the neck, thorax, and 
right arm, he. terminate in the right subclavi- 
an vein. 

As the lymphatics commonly lie close to the 
large blood-vessels, a ligature passed round 
the crural artery in a living animal, by includ- 
ing the lymphatics, will occasion a distention 
of these vessels below the ligature, so as to de- 
monstrate them with ease ; and a ligature pass- 
ed round the thoracic duct, instantly after kill- 
ing an animal, will, by stopping the course of its 
contents into the subclavian vein, distend not 
only ;he lacteals, but also the lymphatics in the 
abdomen and lower extremities, with their na- 
tural fluids. * 

The coats of these vessels are too thin to be 
separated from each other ; but the mercury 
they are capable of sustaining, proves them to 
be very strong ; and their great power of con- 
traction, after undergoing considerable disten- 
tion, together with the irritability with which 
Baron Haller found them to be enduedf, seems 

N n 

* In the dead body they may be easily demonstrated by open- 
ing the artery ramifying through any viscus, as in the spleen, 
for instance, and then throwing in air ; by which the lymphatics 
will be distended. One of them may then be punctured, and 
mercury introduced into it through a blow-pipe. 
f Sur le movement du sang Ex. 295, 298. 



282 Of the Abdomen. 

to render it probable, that, like the blood-ves- 
sels, they have a muscular coat. 

The lymphatics are nourished after the same 
manner as all the other parts of the body. For 
even the most minute of these vessels are pro- 
bably supplied with still more minute arteries 
and veins. This seems to be proved by the 
inflammation of which they are susceptible ; 
and the painful swellings which sometimes 
take place in lymphatic vessels, prove that 
they have nerves as well as blood-vessels. 

Both the lacteals, lymphatics, and thoracic 
duct, are furnished with valves, which are 
much more common in these vessels than in 
the red veins. These valves are usually in 
pairs, and serve to promote the course of the 
chyle and lymph towards the thoracic duct, and 
to prevent its return. Mention has been made 
of the glands, through which the lacteals pass 
in their course through the mesentery ; and it 
is to be observed, that the lymphatics pass 
through similar glands in their way to the tho- 
racic duct. These glands are all of a conglo- 
bate kind, but the changes which the chyle and 
lymph undergo in their passage through them,, 
have not yet been ascertained. 

The lymphatic vessels begin from surfaces 
and cavities in all parts of the body as absorb- 
ents. This is a fact now universally allowed ; 
but how the fluids they absorb are poured into 
those cavities, is a subject of controversy. The 
contents of the abdomen, for instance, were 
described as being constantly moistened by a 
very thin watery fluid. The same thing takes 
place in the pericardium, pleura, and all the 



Of the Abdomen. 283 

other cavities of the body, and this watery flu- 
id is the lymph. But whether it is exhaled into 
those cavities through the minute ends of arte- 
ries, or transuded through their coats, are the 
points in dispute. We cannot here be permit- 
ted to relate the many ingenious arguments 
that have been advanced in favour of each of 
these opinions ; nor is it perhaps of conse- 
quence to our present purpose to enter into the 
dispute. It will be sufficient if the reader can 
form an idea of what the lymph is, and of the 
manner in which it is absorbed. 

The lymph, from its transparency and want 
of colour, would seem to be nothing but wa- 
ter; and hence the first discoverers of these 
vessels styled them ductus aquosi; but experi- 
ments prove, that the lymph of an healthy ani- 
mal coagulates by being exposed to the air, 
or a certain degree of heat, and likewise by be- 
ing suffered to rest.; seeming to agree in this 
property with that part of the blood called the 
coagulable lymph. — This property of the lymph 
leads to determine its use, in moistening and 
lubricating the several cavities of the body in 
which it is found ; and for which, by its gela- 
tinous principle, it seems to be much better 
calculated than a pure and watery fluid would 
be, for such it has been supposed to be by 
some anatomists. 

The mouths of the lymphatics and lacteals^hy 
acting as capillary tubes, seem to absorb the 
lymph and chyle somewhat in the same manner 
as a capillary tube of glass, when put into a ba- 
son of water, is enabled to attract the water into 
it to a certain height ; but it is probable that they 



284 Of the Abdomen. 

likewise possess a living power, which assists 
in performing this office. In the human body 
the lymph, or the chyle, is probably conveyed 
upon this principle as far as the first pair of 
valves, which seem to be placed not far from 
the orifice of the absorbing vessel, whether 
lymphatic or lacteal ; and the fluid will then be 
propelled forwards, by a continuation of the 
absorption at the orifice. But this does not 
seem to be the only inducement to its progress 
towards the thoracic duct ; these vessels have 
probably a muscular coat, which may serve to 
press the fluid forwards from one pair of valves 
to another ; and as the large lymphatic vessels* 
and the thoracic duct are placed close to the 
large arteries, which have a considerable pul- 
sation, it is reasonable to suppose, that they 
derive some advantages from this situation. 



Sect. XV. Of the Generative Organs; of 
Conception, &c. 

§. 1. The Male Organs. 

The male organs of generation have been 
usually divided into the parts which serve to 
prepare the semen from the blood, and those 
which are distended to convey it into the womb> 
But it seems to be more proper to distinguish 
them into the preparing, the containing, and 
the expelling parts, which are the different 
offices of the testes, the vesiculce seminales, and 
the penis ; and this is the brder in which we 
propose to describe them. 



Of the Abdomen. 285 

The testes are two glandular bodies, serving 
to secrete the semen from the blood. They 
are originally formed and lodged within the ca- 
vity of the abdomen ; and it is not till after 
the child is born, or very near that time, that 
they begin to pass into the groin, and from 
thence into the scrotum.* By this disposition 
they are very wisely protected from the inju- 
ries to which they would be liable to be ex- 
posed, from the different positions of the child 
at the time of parturition. 

The testicles in this state are loosely at- 
tached to the psoae muscles, by means of the 
peritonaeum by which they are covered ; and 
they are at this time of life connected in a 
very particular manner to the parietes of the 
abdomen, and likewise to the scrotum, by 
means of a substance which Mr. Hunter calls 
the ligament or gubernaculum testis, because it 
connects the testis with the scrotum, and di- 
rects its course in its descent. This guber- 

* It sometimes happens in dissecting ruptures, that the intes- 
tine is found in the same sac, and in contact with the testis. 
This appearance was at fir^t attributed to a supposed laceration 
of the peritonaeum ; but later observations, by pointing out the 
situation of the testicles in the foetus, have led to prove, that 
the testis, as it descends into the scrotum, carries with it a por- 
tion or elongation of the peritonaeum, which becomes its tunica 
vaginalis, or a kind of sac, in which the testicle is lodged, as 
will be explained in the course of this section. The communica- 
tion between this sac and the cavity of the abdomen, is usually 
soon cut off; but in some subjects it continues open during life ; 
and when an hernia or descent of the intestine takes place in such 
a subject, it does not push down a portion of the peritonaeum 
before it, as it must otherwise necessarily do, but passes at once 
through this opening, and comes in contact with the n iked tes- 
ticle, constituting that particular species of rupture called hernia 
congenita. 



286 Of the Abdomen. 

naculum is of* a pyramidal form, with its bul- 
bous head fixed to the lower end of the testis 
and epididymis, and loses its lower and slen- 
der extremity in the cellular membrane of the 
scrotum. It is difficult to ascertain what the 
structure and composition of this gubernacu- 
lum is, but it is certainly vascular and fibrous ; 
and, from certain circumstances, it would seem 
to be in part composed of the cremaster mus- 
cle, running upwards to join the lower end 
of the testis. 

We are not to suppose that the testicle, 
when descended into the scrotum, is to be 
seen loose as a piece of gut or omentum 
would be in a common hernial sac. We have 
already observed, that during its residence in 
the cavity of the abdomen it is attached to the 
peritonaeum, which descends with it ; so that 
when the sac is completed in the scrotum, the 
testicle is at first attached only to the posterior 
part of it, while the fore part of it lies loose, 
and for some time affords a communication 
with the abdomen. The spermatic chord, 
which is made up of the spermatic artery and 
vein, and of the vas deferens or excretory duct 
of the testis, is closely attached behind to the 
posterior part of this elongation of the perito- 
naeum- But the fore part of the peritoneal 
sac, which is at first loose and not attached to 
the testicle, closes after a certain time, and 
becomes united to the posterior part, and thus 
perfectly surrounds the testicle as it were in 
a purse. 

The testicles of the foetus differ only in their 
size and situation from those of the adult. In 



Of the Abdomen. 28 7 

their passage from the abdomen they descend 
through the abdominal rings into the scrotum, 
where they are supported and defended by va- 
rious integuments. 

What the immediate cause of this descent 
is, has not yet been satisfactorily determined. 
It has been ascribed to the effects of respira- 
tion, but the testicles have sometimes been 
found in the scrotum before the child has 
breathed ; and it does not seem to be occasi- 
oned by the action of the cremaster muscle, 
because the same effect would be liable to 
happen to the hedge-hog, and some other 
quadrupeds, whose testicles remain in the ab- 
domen during life. 

The scrotum, which is the external or com- 
mon covering of both testicles, is a kind of sac 
formed by the common integuments, and ex- 
ternally divided into two equal parts by a pro- 
minent line called raphe. 

In the inner part of the scrotum we meet 
with a cellular coat called dartos,* which by 
its duplicature divides the scrotum into two 
equal parts, and forms what is called septum 
scroti, which corresponds with the raphe. 
The collapsion which is so often observed to 
take place in the scrotum of the healthy sub- 
ject, when excited by cold or by the stimulus 
of venery, seems to be very properly attribut- 

* The dartos has usually been considered as a muscle, and is 
described as such both by Douglas and Wir.slow. But there 
being no part of the scrotum of the human subject which can be 
said to consist of muscular fibres, Albinus and Haller have very 
properly omitted to describe the dartos as a muscle, and consider 
it mcrelv as a cellular coat. 



288 Of the Abdomen. 

ed to the contractile motion of the skin, and 
not to any muscular fibres, as is the case in 
dogs and some other quadrupeds. 

The scrotum, then, by means of its septum, 
is found to make two distinct bags, in which 
the testicles, invested by their proper tunics, 
are securely lodged and separated from each 
other. These coats are the cremaster, the 
tunica vaginalis, and the tunica albuginea. 
The first of these is composed of muscular 
fibres, and is to be considered only as a par- 
tial covering of the testis ; for it surrounds 
only the spermatic chord, and terminates upon 
the upper and external parts of the tunica va- 
ginalis testis, serving to draw up and suspend 
the testicle.* The tunica vaginalis testis has 
already been described as being a thin pro- 
duction of the peritonaeum, loosely adhering 
every where to the testicle, which it includes 
as it were in a bag. The tunica albuginea is 
a firm, white, and very compact membrane 
of a glistening appearance, which immediate- 
ly invests the body of the testis and the epidi- 
dymus ; serving in some measure to connect 
them to each other, but without extending 
itself at all to the spermatic chord. This tu- 
nica albuginea serves to confine the growth 
of the testis and epididymus within certain 
limits, and by giving them a due degree of 
firmness, enables them to perform their pro- 
per functions. 

* The cremaster muscle is composed of a ftw fibres from the 
obliquus interims abdominis, which uniting with a few from the 
transversalis, descend upon the spermatic chord, and are insen- 
sibly lost upon the tunica vaginalis of the testicle. It serves to 
suspend and draw up the testicle. 



Of the Abdomen, 289 

Having removed this last tunic, we disco- 
ver the substance of the testicle itself, which 
appears to be made up of an infinite number 
of very elastic filaments, which may be best 
distinguished after macerating the testicle in 
water. Each testicle is made up of the sper- 
matic artery and vein, and the excretory ves- 
sels or tubuli seminiferi. There are likewise 
a great number of absorbent vessels, and some 
branches of nerves to be met with in the tes- 
ticles. 

The spermatic arteries arise one on each 
side from the aorta, generally about an inch 
below the emulgents. The right spermatic 
vein commonly passes into the vena cava ; but 
the left spermatic vein usually empties itself 
into the emulgent on that side ; and it is sup- 
posed to take this course into the emulgent, 
that it may avoid passing over the aorta, which 
it would be obliged to do in its way to the 
vena cava. 

The blood is circulated very slowly through 
the spermatic artery, which makes an infinite 
number of circumvolutions in the substance of 
the testicle, where it deposites the semen, 
which passes through the tubuli seminiferi. 
These tubuli seminiferi are seen running in 
short waves from the tunica albuginea to the 
axis of the testicle ; and are divided into dis- 
tinct portions by certain thin membranous pro- 
ductions, which originate from the tunica al- 
buginea. They at length unite, and by an 
infinite number of convolutions form a sort of 

Oo 



290 Of the Abdomen. 

appendix to the testis called epididymis,* which 
is a vascular body of an oblong shape, situate 
upon the superior part of each testicle. These 
tubuli of the epididymis at length form an ex- 
cretory duct called vas deferens, which as- 
cends towards the abdominal rings, with the 
other parts that make up the spermatic chord, 
and then a separation takes place ; the nerves 
and blood-vessels passing on to their several 
terminations, and the vas deferens going to 
deposite its semen in the vesiculse seminales, 
which are two soft bodies of a white and con- 
voluted appearance externally, situated ob- 
liquely between the rectum and the lower 
part of the bladder, and uniting together at 
the lower extremity. From these reservoirs,! 

* The testicles were named didytni by the ancients, and the 
name of this part was given to it on account of its situation upon 
the testicle. 

•f That the bags called vesicula seminales are reservoirs of se- 
men, is a circumstance which has been by anatomists universal- 
ly believed. Mr. J. Hunter, however, from several circumstan- 
ces, has been induced to think this opinion erroneous. 

He has examined these vesiculse in people who have died sud- 
denly, and he found their contents to be different in their proper- 
ties from the semen. In those who had lost one of the testicles, 
or the use of one of them, by disease, both the vesiculce were 
full, and their contents similar. And in a lusus nature, where 
there was no communication between the vasa deferentia and ve- 
siculse, nor between the vesiculse and penis, the same thing took 
place. 

From these observations, he thinks we have a presumptive 
proof, That the semen can be absorbed in the body of the testi- 
cle and in the epididymis, and that the vesiculse secrete a mucus 
which they are capable of absorbing when it cannot be made use 
of: That the semen is not retained in reservoirs after it is secret- 
ed, and kept there till it is used ; but that it is secreted at the 
time, in consequence of certain affections of the mind stimulat- 
ing the testicles to this action. 

He corroborates his observations by the appearance on dissec- 
tion in other animals ; and here he finds, That the shape and 



Of the Abdomen. 291 

which are plentifully supplied with blood-ves- 
sels and nerves, the semen is occasionally dis- 
charged through two short passages, which 
open into the urethra close to a little eminence 
called verumontamim. 



contents of the vesiculas vary much in different animals, while 
the semen in most of them he has examined is nearly the same : 
That the vasa deferentia in many animals do not communicate 
with the vesicular : That the contents of the vesicuke of castrated 
and perfect animals are similar, and nearly equal in quantity, in 
no way resembling the semen as emitted from the animal in 
coitu, or what is found in the vas deferens after death. He ob- 
serves likewise, that the bulb of the urethra of perfect males is 
considerably larger than in castrated animals. 

From the whole, he thinks the following inferences may he 
fairly drawn : That the bags called vesicula seminaks are not se- 
minal reservoirs, but glands secreting a peculiar mucus ; and 
that the bulb of the urethra is properly speaking the receptacle 
of the semen, in which it is accumulated previous to ejection. 

But although he has endeavoured to prove that the vesicular 
do not contain the semen, he has not been able to ascertain their 
particular use. He thinks, however, we may be allowed upon 
the whole to conclude, that they are, together with other parts, 
subservient to the purposes of generation. 

Although the author has treated this subject very ably, and 
made many ingenious observations, some things may be object- 
ed to what he has advanced ; of which the following are a few; 
That those animals who have bags called vesicula seminaks per- 
form copulation quickly ; whereas others that want them, as in 
the dog kind, are tedious in copulation: That in the human 
body, at least, there is a free communication between the vasa 
deferentia and vesicuke ; and in animals where the author has 
observed no communication between the vasa deferentia and ve- 
sicular, there may be a communication by vessels not yet disco- 
vered, and which may be compared to the hepato-cystic ducts 
in fowls and fishes : That the fluid in the end of the vasa defe- 
rentia and the vesicular seminales are similar, according to the 
author's own observation.: That the vesicular in some animals 
increase and decrease with the testicle at particular seasons : 
That in birds and certain fishes, there is a dilatation of the ends 
of the vasa deferentia, which the author himself allows to be a 
reservoir for the semen. 

With respect to the circumstance of the bulb of the urethra 
answering the purpose of a reservoir, the author has mentioned 
no facts which tend to establish this opinion. See Observations 
on certain Parts of the Animal Otconomj. 



292 Of the Abdomen. 

Near this eminence we meet with the pros- 
tate, which is situated at the neck of the blad- 
der, and is described as being of a glandular 
structure. It is shaped somewhat like a heart 
with its small end foremost, and invests the 
origin of the urethra. Internally it appears to 
be of a firm substance, and composed of seve- 
ral follicles, secreting a whitish viscid fluid, 
that is discharged by ten or twelve excretory 
ducts into the urethra, on each side of the 
openings of the vesicular seminales at the same 
time, and from the same causes that the semen 
is expelled. As this latter fluid is found to be 
exceedingly limpid in the vesiculse seminales 
of the dead subject, it probably owes its white- 
ness and viscidity to this liquor of the pros- 
tate. 

The penis, which is to be considered as 
the vehicle or active organ of procreation, is 
composed of two columns, the corpora caver- 
nosa, and corpus spongiosum. The corpora 
cavernosa, which constitute the greatest part 
of the penis, may be described as two cylin- 
drical ligamentous tubes, each of which is 
composed of an infinite number of minute cells 
of a spongy texture, which communicate with 
each other. These two bodies are of a very 
pliant texture, and capable of considerable 
distention; and being united laterally to each 
other, occasion by this union a space above 
and another below. The uppermost of these 
spaces is filled by the blood-vessels, and the 
lower one, which is larger than the other, by 
the urethra and its corpus spongiosum. These 
two cavernous bodies are at first only separat- 



Of the Abdomen. 293 

ed by a partition of tendinous fibres, which 
allow them to communicate with each other ; 
but they afterwards divaricate from each other 
like the branches of the letter Y, and diminish- 
ing gradually in size, are attached, one on 
each side, by means of the ligamentum sus- 
pensorium penis to the ramus ischii, and to 
the inferior portion of the os pubis. 

The corpus spongiosum penis, or corpus 
spongiosum urethras, as it is styled by some 
authors, begins as soon as the urethra has 
passed the prostate, with a thick origin almost 
like a heart, first under the urethra, and af- 
terwards above it, becoming gradually thin- 
ner, and surrounding the whole canal of the 
urethra, till it terminates in a considerable ex- 
pansion, and constitutes what is called the 
glans penis, which is exceedingly vascular, and 
covered with papillse like the tongue. The 
cuticle which lines the inner surface of the ure- 
thra, is continued over the glans in the same 
manner as it is spread over the lips. 

The penis is invested by the common inte- 
guments, but the cutis is reflected back every 
where from the glans as it is in the eye-lids; 
so that it covers this part, when the penis is in 
a relaxed state, as it were with a hood, and 
from this use is called prepuce. 

The prepuce is tied down to the under part 
of the glans by a small ligament called franum, 
which is in fact only a continuation of the cu- 
ticle and cutis. There are many simple seba- 
ceous follicles called glandule odorifera.\ 
placed round the basis of the glans ; and the 
fluid they secrete serves to preserve the exqui- 



294 Of the Abdomen. 

site sensibility of this part of the penis, and to 
prevent the ill effects of attrition from the pre- 
puce. 

The urethra may be denned to be a mem- 
branous canal, passing from the bladder 
through the whole extent of the penis, Seve- 
ral very small openings, called lacuna;, com- 
municate with this canal, through which a mu- 
cus is discharged into it ; and besides these, 
there are two glands, first described by Cow- 
per, as secreting a fluid for lubricating the 
urethra, and called Cowper's glands ;* and 
Littref speaks of a gland situated near the 
prostate, as being destined for the same use. 

The urethra being continued from the neck 
of the bladder, is to be considered as making 
part of the urinary passage ; and it likewise 
affords a conveyance to the semen, which we 
have observed is occasionally discharged into 
it from the vesiculse seminales. The direc- 
tion of this canal being first under and then 
before the pubis, occasions a winding in its 
course from the bladder to the penis not unlike 
the turns of the letter S. 

The penis has three pair of muscles, the 
erectores, acceleratores, and transversales. 
They push the blood from the crura to the fore 
part of the corpora cavernosa. The first origi- 
nate from the tuberosity of the ischium, and 
terminate in the corpora cavernosa. The ac- 
celeratores arise from the sphincter, and by 

* Both Heister and Morgagni observe, that they have some- 
times not been able to find these glands : so that they do not 
seem to exist in all subjects. 

f Memoires de 1' Acad. Royale des Sciences, 1 700. 



Of the Abdomen. 295 

their insertion serve to compress the bulbous 
part of the urethra ; and the transversales are 
destined to afford a passage to the semen, by- 
dilating the canal of the urethra. 

The arteries of the penis are chiefly deriv- 
ed from the internal iliacs. Some of them are 
supposed to terminate by pabulous orifices 
within the corpora cavernosa and corpus spon- 
giosum ; and others terminate in veins, which 
at last make up the vena magna dorsi penis, 
and other smaller veins, which are in general 
distributed in like order with the arteries. 

Its nerves are large and numerous. They 
arise from the great sciatic nerve, and accom- 
pany the arteries in their course through the 
penis. 

We have now described the anatomy of this 
organ ; and there only remains to be explain- 
ed, how it is enabled to attain that degree of 
firmness and distention which is essential to 
the great work of generation. 

The greatest part of the penis has been 
spoken of as being of a spongy and cellular 
texture, plentifully supplied with blood-vessels 
and nerves, and as having muscles to move 
it in different directions. Now, the blood is 
constantly passing into its cells through the 
small branches of the arteries which open into 
them, and is from thence as constantly return- 
ed by the veins, so long as the corpora caver- 
nosa and corpus spongiosum continue to be in 
a relaxed and pliant state. But when, from 
any nervous influence, or other means, which 
it is not necessary here to define or explain, 
the erectores penis, ejaculatores seminis, le- 



296 Of the Abdomen. 

vatorcs ani, h.c. are induced to contract, the 
veins undergo a certain degree of compres- 
sion, and the passage of the blood through 
them is so much impeded, that it collects in 
them in a greater proportion than they arc 
enabled to carry off, so that the penis gradu- 
ally enlarges ; and being more and more for- 
cibly drawn up against the os pubis, the vena 
magna itself is at length compressed, and the 
penis becomes fully distended. But as the 
causes which first occasioned this distention 
subside, the penis gradually returns to its state 
of relaxation. 

\. 2. Female Organs of Generation. 

Anatomical writers usually divide the fe- 
male organs of generation into external and in- 
ternal. In the first division they include the 
mons veneris , labia pudendi, perineum, clito- 
ris, nymphts, and caruncula myrtiformes ; and 
in the latter, the vagina, with the uterus and 
its appendages. 

The mons veneris, which is placed on the 
upper part of the symphysis pubis, is inter- 
nally composed of adipose membranes, which 
makes it soft and prominent : it divides into 
two parts called labia pudendi, which descend- 
ing towards the rectum, from which they are 
divided by the perinaeum, form what is called 
the fourchette. The perinseum is that fleshy 
space which extends about an inch and an half 
from the fourchette to the anus, and from 
thence about two inches to the coccyx. 



Of the Abdomen. 297 

The labia pudendi being separated, we ob- 
serve a sulcus called fossa magna; in the up- 
per part of which is placed the clitoris, a small 
round spongy body, in some measure resem- 
bling the male penis, but impervious, com- 
posed of two corpora cavernosa, arising from 
the tuberosities of the ossa ischii; furnished 
with two pair of muscles, the erectores elito- 
ridis, and the sphincter or constrictor ostii va- 
ginae ; and terminating in a glans, which is 
covered with its prepuce. From the lower 
part, on each side of the fossa, pass the nyir*- 
phse, two membranous and spongy folds which 
seem destined for useful purposes in parturi- 
tion, by tending to enlarge the volume of the 
vagina as the child's head passes through it. 
Between these, about the middle of the fossa 
magna, we perceive the orifice of the vagina or 
os externum, closed by folds and wrinkles ; 
and about half an inch above this, and about 
an inch below the clitoris, appears the meatus 
urinarius or orifice of the urethra, much short- 
er, though somewhat larger, than in men, 
with a little prominence at its lower edge, 
which facilitates the introduction of the ca- 
theter. 

The os externum is surrounded internally 
by several membranous folds called carunculce 
myrtiformes, which are partly the remains of 
a thin membrane called hymen, that covers 
the vagina in children. In general the hymen 
is sufficiently open to admit the passage of the 
menses, if it exists at the time of their appear- 
ance ; sometimes, however, it has been found 
perfectly closed. 

p P 



298 Of the Abdomen. 

The vagina, situated between the urethra 
and the rectum, is a membranous cavity, sur- 
rounded especially at its external extremity 
with a spongy and vascular substance, which 
is covered by the sphincter ostii vaginae. It 
terminates in the uterus, about half an inch 
above the os tincee, and is wider and shorter 
in women who have had children than in vir- 
gins. 

All these parts are plentifully supplied with 
blood-vessels and nerves. Around the nym- 
phae there are sebaceous follicles, which pour 
out a fluid to lubricate the inner surface of the 
vagina ; and the meatus urinarius, like the 
urethra in the male subject, is constantly 
moistened by a mucus, which defends it against 
the acrimony of the urine. 

The uterus is a hollow viscus, situated in 
the hypogastric region, between the rectum 
and bladder. It is destined to receive the first 
rudiments of the foetus, and to assist in the 
developement of all its parts, till it arrives at 
a state of perfection, and is fitted to enter into 
the world, at the time appointed by the wise 
Author of nature. 

The uterus, in its unimpregnated state, re- 
sembles a pear in shape, somewhat flattened, 
with its fundus or bottom part turned towards 
the abdomen, and its cervix or neck surround- 
ed by the vagina. The entrance into its ca- 
vity forms a little protuberance, which has 
been compared to the mouth of a tench, and 
is therefore called os tinea. 

The substance of the uterus, which is of a 
considerable thickness, appears to be com- 



Of the Abdomen. 299 

posed of muscular and small ligamentous fi- 
bres, small branches of nerves, some lym- 
phatics, and with arteries and veins innumera- 
ble. Its nerves are chiefly derived from the 
intercostal, and its arteries and veins from the 
hypogastric and spermatic. The membrane 
which lines its cervix, is a continuation of the 
inner membrane of the vagina ; but the outer 
surface of the body of the uterus is covered 
with the peritonaeum, which is reflected over 
it, and descends from thence to the intestinum 
rectum. This duplicature of the peritonaeum, 
by passing off from the sides of the uterus to 
the sides of the pelvis, is there firmly con- 
nected, and forms what are called ligamenta 
uteri lata ; which not only serve to support 
the uterus, but to convey nerves and blood- 
vessels to it. 

The ligamenta uteri rotunda arise from the 
sides of the fundus uteri, and passing along 
within the fore-part of the ligamenta lata, de- 
scend through the abdominal rings, and ter- 
minate in the substance of the mons veneris. 
The substance of these ligaments is vascular, 
and although both they and the ligamenta lata 
admit the uterus in the virgin state, to move 
only about an inch up and down, yet in the 
course of pregnancy they admit of consider- 
able distention, and after parturition return 
nearly to their original state with surprising 
quickness. 

On each side of the inner surface of the 
uterus, in the angle near the fundus, a small 
orifice is to be discovered, which is the begin- 
ning of one of the tubae Fallopianae. Each of 



3 00 Of the Abdomen. 

these tubes, which are two in number, passing 
through the substance of the uterus, is extend- 
ed along the broad ligaments, till it reaches the 
edge of the pelvis, from whence it reflects 
back ; and turning over behind the ligaments, 
about an inch of its extremity is seen hanging 
loose in the pelvis, near the ovarium. These 
extremities, having a jagged appearance, are 
called jimbrite, or morsus diaboli. Each tuba 
Fallopiana is usually about three or four inches 
long. Their cavities are at first very small, 
but become gradually larger, like a trumpet, 
as they approach the fimbriae. 

Near the fimbriae of each tuba Fallopiana, 
about an inch from the uterus, is situated an 
oval body called ovarium, of about half the 
size of the male testicle. Each of these ovaria 
is covered by a production of the peritonaeum, 
and hangs loose in the pelvis. They are of a 
flat and angular form, and appear to be com- 
posed of a white and cellular substance, in 
which we are able to discover several minute 
vesicles filled with a coagulable lymph, of an 
uncertain number, commonly exceeding 12 in 
each ovary. In the female of riper years, 
these vesicles become exceedingly turgid, and 
a kind of yellow coagulum is gradually formed 
within one of them, which increases for a cer- 
tain time. In conception, one of these mature 
ova is supposed to be impregnated with the 
male semen, and to be squeezed out of its 
nidus into the Fallopian tube ; after which the 
ruptured part forms a substance which in some 
animals is of a yellow colour, and is therefore 
called corpus luteum; and it is observable, that 



Of the Abdomen. 301 

the number of these scars or fissures in the 
ovarium, constantly corresponds with the num- 
ber of foetuses excluded by the mother. 



§. 3. Of Conception. 

Man, being ever curious and inquisitive, 
has naturally been led to inquire after the origin 
of his existence ; and the subject of generation 
has employed the philosophical world in all 
ages : but in following nature up to her mi- 
nute recesses, the philosopher soon finds him- 
self bewildered, and his imagination often sup- 
plies that which he so eagerly wishes to disco- 
ver, but which is destined perhaps never to be 
revealed to him. Of the many theories which 
have been formed on this subject, that of the 
ancient philosophers seems to have been the 
most simple : they considered the male semen 
as alone capable of forming the fcetus, and be- 
lieved that the female only afforded it a lodging 
in the womb, and supplied it with nourishment 
after it was perfectly formed. This opinion, 
however, soon gave place to another, in which 
the female was allowed a more considerable 
share in conception. 

This second system considered the fcetus 
as being formed by the mixture of the semi- 
nal liquor of both sexes, by a certain arrange- 
ment of its several particles in the uterus. 
But in the 16th century, vesicles or eggs were 
discovered in the ovaria or female testicles ; 
the fcetus had been found sometimes in the ab- 
domen, and sometimes in the Fallopian tubes ; 



302 Of the Abdomen. 

and the two former opinions were exploded in 
favour of a new doctrine. The ovaria were 
compared to a bunch of grapes, being suppos- 
ed to consist of vesicles, each of which had a 
stalk ; so that it might be disengaged without 
hurting the rest, or spilling the liquor it con- 
tained. Each vesicle was said to include a lit- 
tle animal, almost complete in all its parts ; and 
the vapour of the male semen being conveyed 
to the ovarium, was supposed to produce a fer- 
mentation in the vesicle, which approached 
the nearest to maturity ; and thus inducing it 
to disengage itself from the ovarium, it passed 
into the tuba Fallopiana, through which it was 
conveyed to the uterus. Here it was supposed 
to take root like a vegetable seed, and to form, 
with the vessels originating from the uterus, 
what is called the placenta ; by means of which 
the circulation is carried on between the mo- 
ther and the foetus. 

This opinion, with all its absurdities, con- 
tinued to be almost universally adopted till the 
close of the same century, when Lieuwen- 
hoeck, by means of his glasses, discovered 
certain opake particles, which he described as 
so many animalcula, floating in the seminal 
fluid of the male. 

This discovery introduced a new schism 
among the philosophers of that time, and gave 
rise to a system which is not yet entirely explod- 
ed. According to this theory the male semen 
passing into the tubse Fallopianse, one of the 
animalcula penetrates into the substance of the 
ovarium, and enters into one of its vesicles or 
ova. This impregnated ovum is then squeez- 



Of the Abdomen. 303 

ed from its husk, through the coats of the ova- 
rium, and being seized by the fimbria?, is con- 
ducted through the tube to the uterus, where 
it is nourished till it arrives at a state of per- 
fection. In this system there is much ingenu- 
ity ; but there are certain circumstances sup- 
posed to take place, which have been hitherto 
inexplicable. A celebrated modern writer, M. 
Buffon, endeavours to restore, in some mea- 
sure, the most ancient opinion, by allowing the 
female semen a share in this office ; asserting, 
that animalcula or organic particles are to be 
discovered in the seminal liquor of both sexes : 
he derives the female semen from the ovaria, 
and he contends that no ovum exists in those 
parts. But in this idea he is evidently mista- 
ken ; and the opinion now most generally 
adopted is, that an impregnation of the ovum, 
by the influence of the male semen, is essential 
to conception.* That the ovum is to be im- 
pregnated, there can be no doubt ; but as the 
manner in which such an impregnation is sup- 
posed to take place, and the means by which the 
ovum afterwards gets into the Fallopian tube, 
and from thence into the uterus, are still found- 
ed chiefly on hypothesis, we will not attempt 
to extend farther the investigation of a sub- 
ject concerning which so little can be advanc- 
ed with certainty. 

* The learned Abbe wSpallanzani has thrown much light on 
this curious subject, and has proved by a variety of experiments, 
that the animalcule exists entire in the female ovum and that the 
male seed is only necessary to vivify and put it in motion.— His 
experiments and observations are worthy the attentive perusal of 
every physiologist. 



o04 Of the Abdomen. 



\. 4. Of the Foetus in Utero. 

Opportunities of dissecting the human 
gravid uterus occurring but seldom, the state 
of the embryo* immediately after conception 
cannot be perfectly known. 

When the ovum descends into the uterus, 
it is supposed to be very minute ; and it is not 
till a considerable time after conception that the 
rudiments of the embryo begin to be ascertain- 
ed. 

About the third or fourth week the eye may 
discover the first lineaments of the foetus ; but 
these lineaments are as yet very imperfect, 
it being only about the size of a house-fly. 
Two little vessels appear in an almost transpa- 
rent jelly ; the largest of which is destined to 
become the head of the foetus, and the other 
smaller one is reserved for the trunk. But at 
this period no extremities are to be seen ; the 
umbilical cord appears only as a very minute 
thread, and the placenta does not as yet absorb 
the red particles of the blood. At six weeks, 
not only the head but the features of the face 
begin to be developed. The nose appears like 
a small prominent line, and we are able to dis- 
cover another line under it, which is destined 
for the separation of the lips. Two black 
points appear in the place of eyes, and two 
minute holes mark the ears. At the sides of 



* The rudiments of the child are usually distinguished by this 
name till the human figure can be distinctly ascertained, and then 
it has the appellation of fetus. 



Of the Abdomen. 305 

the trunk, both above and below, we see four 
minute protuberances, which are the rudiments 
of the arms and legs. At the end of eight 
weeks the body of the foetus is upwards of an 
inch in length, and both the hands and feet are 
to be distinguished. The upper extremities 
are found to increase faster than the lower ones, 
and the separation of the fingers is accomplish- 
ed sooner than that of the toes. 

At this period the human form may be de- 
cisively ascertained ; — all the parts of the face 
may be distinguished, the shape of the body 
is clearly marked out, the haunches and the 
abdomen are elevated, the fingers and toes are 
separated from each other, and the intestines 
appear like minute threads. 

At the end of the third month, the foetus 
measures about three inches; at the end of the 
fourth month, five inches ; in the fifth month, 
six or seven inches ; in the sixth month, eight 
or nine inches ; in the seventh month, eleven or 
twelve inches ; in the eighth month, fourteen 
or fifteen inches ; and at the end of the ninth 
month, or full time, from eighteen to twenty- 
two inches. But as we have not an opportu- 
nity of examining the same foetus at different 
periods of pregnancy, and as their size and 
length may be influenced by the constitution 
and mode of life of the mother, calculations of 
this kind must be very uncertain. 

The foetus during all this time assumes an 
oval figure, which corresponds with the shape 
of the uterus. Its chin is found reclining on 
its breast with its knees drawn up towards its 
chin, and its arms folded over them. But it 

Qq 



306 Of the Abdomen. 

seems likely, that the posture of some of these 
parts is varied in the latter months of pregnan- 
cy, so as to cause those painful twitches which 
its mother usually feels from time to time. In 
natural cases, its head is probably placed to- 
wards the os tincse from the time of conception 
to that of its birth ; though formerly it was con- 
sidered as being placed towards the fundus ute- 
ri till about the eighth or ninth month, when 
the head, by becoming specifically heavier 
than the other parts of the body, was supposed 
to be turned downwards. 

The capacity of the uterus increases in pro- 
portion to the growth of the foetus, but with- 
out becoming thinner in its substance, as might 
naturally be expected. The nourishment of 
the foetus, during all this time, seems to be de- 
rived from the placenta, which appears to be 
originally formed by that part of the ovum 
which is next the fundus uteri. The remain- 
ing part of the ovum is covered by a mem- 
brane called spongy chorion ;* within which is 
another called true chorion, which includes a 
third termed amnios :f this contains a watery 

* Dr. Hunter has described this as a lamella from the inner 
surface of the uterus. In the latter months of pregnancy it be- 
comes gradually thinner and more connected with the chorion : 
he has named it membrana caduca, or decidua, as it is cast off with 
the placenta. Signior Scarpa, with more probability, considers 
it as being composed of an inspissated coagulable lymph. 

f In some quadrupeds, the urine appears to be conveyed from 
the bladder through a canal called urachus to the allantou, which 
is a reservoir, resembling a long and blind gut, situated between 
the chorion and amnios. The human foetus seems to have no 
such reservoir, though fome writers have supposed that it does 
exist. From the top of the bladder a few longitudinal fibres are 
extended to the umbilical chord ; and these fibres have been con- 
sidered as the urachus, though without having been ever found 
pervious. 



Of the Abdomen- 307 

fluid which is the liquor amnii,* in which the 
foetus floats till the time of its birth. On the 
side next the foetus, the placenta is covered by 
the amnios and true chorion ; on the side next 
the mother it has a production continued from 
the spongy chorion. The amnios and chorion 
are remarkably thin and transparent, having 
no blood-vessels entering into their composi- 
tion. The spongy chorion is opake and vas- 
cular. 

In the first months of pregnancy, the involu- 
cra bear a large proportion to their contents ; 
but this proportion is afterwards reversed, as 
the foetus increases in bulk. 

The placenta, which is the medium through 
which the blood is conveyed from the mother 
to the foetus, and the manner in which this 
conveyance takes place, deserve next to be 
considered. 

The placenta is a broad, flat, and spongy 
substance, like a cake, closely adhering to the 
inner surface of the womb, usually near the 
fundus, and appearing to be chiefly made up 
of the ramifications of the umbilical arteries 
and vein, and partly of the extremities of the 
uterine vessels. The arteries of the uterus 
discharge their contents into the substance of 

* The liquor amnii coagulates like the lymph. It has been 
supposed to pass into the oesophagus, and to afford nourishment 
to the foetus; but this does not feem probable. Children have 
come into the world without an oesophagus, or any communica- 
tion between the stomach and the mouth ; but there has been no 
well attested instance of a child's having been born without a pla- 
centa ; and it does not seem likely, that any of the fluid can be 
absorbed through the pnres of the skin, the skin in the foetus be- 
ing every where covered with a great quantity of mucus. 



308 Of the Abdomen. 

this cake ; and the veins of the placenta, re- 
ceiving the blood either by a direct communi- 
cation of vessels, or by absorption, at length 
form the umbilical vein, which passes on to 
the sinus of the vena porta?, and from thence 
to the vena cava, by means of the canalis veno- 
sus, a communication that is closed in the 
adult. But the circulation of the blood through 
the heart is not conducted in the foetus as in 
the adult : in the latter, the blood is carried 
from the right auricle of the heart through the 
pulmonary artery, and is returned to the left 
auricle by the pulmonary vein ; but a dilatation 
of the lungs is essential to the passage of the 
blood through the pulmonary vessels, and this 
dilatation cannot take place till after the child is 
born and has respired. This deficiency, how- 
ever, is supplied in the foetus by the immedi- 
ate communication between the right and left 
auricle, through an oval opening, in the septum 
which divides the two auricles, called foramen 
ovale. The blood is likewise transmitted from 
the pulmonary artery to the aorta, by means 
of a duct called canalis arteriosus, which, like 
the canalis venosus, and foramen ovale, gra- 
dually closes after birth. 

The blood is returned again from the foetus 
through two arteries called the umbilical arte- 
ries, which arise from the iliacs. These two 
vessels taking a winding course with the vein, 
form with that, and the membranes by which 
they are surrounded, what is called the um- 
bilical chord. These arteries, after ramifying 
through the substance of the placenta, dis- 
charge their blood into the veins of the uterus ; 










V 




. - 



















Of the Abdomen. 509 

in the same manner as the uterine arteries dis- 
charged their blood into the branches of the 
umbilical vein. So that the blood is constant- 
ly passing in at one side of the placenta and 
out at the other ; but in what particular man- 
ner it gets through the placenta is a point not 
yet determined. 



EXPLANATION of PLATES XXV. 
XXVI. and XXVII. 



Plate XXV. 

Fig. 1. Shows the Contents of the Thorax and 
Abdomen in situ. 

1. Top of the trachea, or wind-pipe. 2 2, 
The internal jugular veins. 3 3, The subcla- 
vian veins. 4, The vena cava descendens. 
5, The right auricle of the heart. 6, The right 
ventricle. 7, Part of the left ventricle. 8, The 
aorta descendens. 9, The pulmonary artery. 
10, The right lung, part of which is cut off to 
show the great blood-vessels. 11, The left 
lung entire. 12 12, The anterior edge of the 
diaphragm. 13 13, The two great lobes of 
the liver. 14, The ligamentum rotundum. 15, 
The gall-bladder. 16, The stomach. 17 17, 
The jejunum and ilium. 18, The spleen. 



310 Of the Abdomen. 



Fig. 2. Shows the Organs subservient of the 
Chylopoietic Viscera, — with those of Urine 
and Generation. 

1 I, The under side of the two great lobes 
of the liver, a, Lobulus Spigelii. 2, The li- 
gamentum rotundum. 3, The gall-bladder. 
4, The pancreas. 5, The spleen. 6 6, The 
kidneys. 7, The aorta descendens. 8, Ve- 
na cava ascendens. 9 9, The renal veins co- 
vering the arteries. 10, A probe under the 
spermatic vessels and a bit of the inferior me- 
senteric artery, and over the ureters. 1111, 
The ureters. 12 12, The iliac arteries and 
veins. 13, The rectum intestinum. 14, The 
bladder of urine. 



Fig. 3. Shows the Chylopoietic Viscera, and 
Organs subservient to them, taken out of 
the Body entire. 

A A, The under side of the two great lobes 
of the liver. B, Ligamentum rotundum. C, 
The gall-bladder. D, Ductus cysticus. E, 
Ductus hepaticus. F, Ductus communis cho- 
ledochus. G, Venaportarum. H, Arteria hep- 
atica. I I, The stomach. K K, Venae and arte- 
riae gastro-epiploicae, dextrae & sinistra. L L, 
Venas St arterise coronariae ventriculi. M, The 
spleen. N N, Mesocolon, with its vessels. 
OOO, Intestinum colon. P, One of the li- 
gaments of the colon, which is a bundle of 
longitudinal muscular fibres. QQ.Q.Q, Jeju- 



Of the Abdomen. 311 

num and ilium. R R, Sigmoid flexure of the 
colon with the ligament continued, and over S, 
The rectum intestinum. T T, Levatores ani. 
U, Sphincter ani. V, The place to which the 
prostate gland is connected. W, The anus. 

Tig. 4. Shows the Heart of a Foetus at the 
full time, with the Right Auricle cut open 
to show the Foramen Ovale, or passage be- 
tween both Auricles. 

a, The right ventricle, b, The left ventri- 
cle, c c, The outer side of the right auricle 
stretched out. d d, The posterior side, which 
forms the anterior side of the septum, e, The 
foramen ovale, with the membrane or valve 
which covers the left side f, Vena cava in- 
ferior passing through g, A portion of the dia- 
phragm. 



Fig. 5. Shows the Heart and Large Vessels 
of a Foetus at the full time. 

a, The left ventricle, b, The right ventri- 
cle, c, A part of the right auricle. d, Left 
auricle, e e, The right branch of the pulmo- 
nary artery, f, Arteria pulmonalis. g g, The 
left branch of the pulmonary artery, with a 
number of its largest branches dissected from 
the lungs, h, The canalis arteriosus, i, The 
arch of the aorta, kk, The aorta descendens. 
1, The left subclavian artery, m, The left ca- 
rotid artery, n, The right carotid artery, o, 
The right subclavian artery, p, The origin 



312 Of the Abdomen, 

of the right carotid and right subclavian arteries 
in one common trunk, q, The vena cava su- 
perior or descendens. r, The right common 
subclavian vein. s, The left common sub- 
clavian vein. 

N. B. All the parts described in this figure 
are to be found in the adult, except the cana- 
lis arteriosus. 



Plate XXVI. 

Fig. 1. Exhibits the more superficial Lympha- 
tic Vessels of the Lower Extremity. 

A, The spine of the os ilium. B, The os 
pubis. C, The iliac artery. D, The knee. 
E, E, F, Branches of the crural artery. G, 
The musculus gastrocnemius. H, The tibia. 
I, The tendon of the musculus tibialis amicus. 
On the out-lines, a, A lymphatic vessel be- 
longing to the top of the foot, b, Its first di- 
vision into branches. c, c, c, Other divisions 
of the same lymphatic vessel. d, A small 
lymphatic gland. e, The lymphatic vessels 
which lie between the skin and the muscles of 
the thigh, f, f, Two lymphat^ glands at the 
upper part of the thigh below the groin. g, 
g, Other glands. h, A lymphatic vessel 
which passes by the side of those glands with- 
out communicating with them ; and, bending 
towards the inside of the groin at (i), opens 
into the lymphatic gland (k). 1, 1, Lympha- 
tic glands in the groin, which are common to 
the lymphatic vessels of the genitals and those 



Of the Abdomen. 313 

of the lower extremity. m, n, A plexus of 
lymphatic vessels passing on the inside of the 
iliac artery. 

Fig. 2. Exhibits a Back View of the lower Ex- 
tremity, dissected so as to show the deeper- 
seated Lymphatic Vessels which accompany 
the Arteries. 

A, The os pubis. B, The tuberosity of 
the ischium. C, That part of the os ilium 
which was articulated with the os sacrum. D, 
The extremity of the iliac artery appearing 
above the groin. E, The knee. F F, The 
two cut surfaces of the triceps muscle, which 
was divided to show the lymphatic vessels that 
pass through its perforation along with the cru- 
ral artery. G, The edge of the musculus gra- 
cilis. H, The gastrocnemius and soleus, much 
shrunk by being dried, and by the soleus be- 
ing separated from the tibia to expose the ves- 
sels. I, The heel. K, The sole of the foot, 
L, The superficial lymphatic vessels passing 
over the knee, to get to the thigh. On the 
out-lines ; M, The posterior tibial artery, a, 
A lymphatic vessel accompanying the posterior 
tibial artery, b, The same vessel crossing the 
artery, c, A small lymphatic gland, through 
which this deep-seated lymphatic vessel passes, 
d, The lymphatic vessel passing under a small 
part of the soleus, which is left attached to the 
bone, the rest being removed. e, The lym- 
phatic vessel crossing the popliteal artery, f, 
g, h, Lymphatic glands in the ham, through 

R r 



314 Of the Abdomen. 

which the lymphatic vessel passes, i, The 
lymphatic vessel passing with the crural ar- 
tery, through the perforation of the triceps 
muscle, k, The lymphatic vessel, after it has 
passed the perforation of the triceps, dividing 
into branches which embrace the artery (1). 
m, A lymphatic gland belonging to the deep- 
seated lymphatic vessel. At this place those 
vessels pass to the fore part of the groin, where 
they communicate with the superficial lym- 
phatic vessels, n, A part of the superficial 
lymphatic vessel appearing on the brim of the 
pelvis. 



Fig. 3. Exhibits the Trunk of the Human 
Subject, prepared to show the Lymphatic 
Vessels and the Ductus Thoracicus. 

A, The neck. B B, The two jugular veins. 
C, The vena cava superior. D D D D, The 
subclavian veins. E, The beginning of the 
aorta, pulled to the left side by means of a li- 
gature, in order to show the thoracic duct be- 
hind it. E, The branches arising from the 
curvature of the aorta. G G, The two caro- 
tid arteries. H H, The first ribs. I I, The 
trachea. K K, The spine. L L, The vena 
azygos. M M, The descending aorta. N, 
T^ie cceliac artery, dividing into three branch- 
es. O, The superior mesenteric artery. P, 
The right crus diaphragmatis. Q Q, The 
two kidneys. R, The right emulgent artery. 
S S, The external iliac arteries, g d, The 
musculi psoae. T, The internal iliac artery- 



Of the Abdomen. 315 

fcj, The cavity of the pelvis. X X, The spine 
of the os ilium. Y Y, The groins. .«, A lym- 
phatic gland in the groin, into which lympha- 
tic vessels from the lower extremity are seen 
to enter, b b, The lymphatic vessels of the 
lower extremities passing under Poupart's li- 
gament, c c, A plexus of the lymphatic ves- 
sels lying on each side of the pelvis, r/, The 
psoas muscle with lymphatic vessels lying 
upon its inside, e, A plexus of lymphatics, 
which having passed over the brim of the pel- 
vis at (c), having entered the cavity of the 
pelvis, and received the lymphatic vessels be- 
longing to the viscera contained in that cavity, 
next ascends, and passes behind the iliac ar- 
tery to (g). f, Some lymphatic vessels of the 
left side passing over the upper part of the os 
sacrum, to meet those of the right side, g, The 
right psoas, with a large plexus of lymphatics 
lying on its inside, h h> The plexus lying on 
each side of the spine, i i ?, Spaces occupied 
by the lymphatic glands, k, The .trunk of. the 
lacteals, lying on the under side of the supe- 
rior mesenteric artery. /, The same dividing 
into two branches, one of which passes on 
each side of the aorta ; that of the right side 
being seen to enter the thoracic duct at (m). 
m, The thoracic duct beginning from the large 
lymphatics, w, The duct passing under the 
lower part of the crus diaphragmatis, and un- 
der the right emulgent artery, o, The thora- 
cic duct penetrating the thorax. ,/>, Some lym- 
phatic vessels joining that duct in the thorax. 
y, The thoracic duct passing under the curva- 
ture of the aorta to get to the left subclavian 



316 Of the Abdomen. 

vein. The aorta being drawn aside to show 
the duct, r, A plexus of lymphatic vessels 
passing upon the trachea from the thyroid 
gland to the thoracic duct. 



Plate XXVII. 

Fig. 1. Represents the Under and Posterior 
Side of the Bladder of Urine, &tc. 

a, The bladder, b b, The insertion of the 
ureters, c c, The vasa deferentia, which con- 
vey the semen from the testicles to d d, The 
vesiculse seminales, — and pass through e, The 
prostate gland, to discharge themselves into 
f, The beginning of the urethra. 

Fig. 2. A transverse Section of the Penis. 

g g, Corpora cavernosa penis, h, Corpus 
cavernosum urethras, i, Urethra, k, Septum 
penis. 1 1, The septum between the corpus 
cavernosum urethrae and that of the penis. 

Fig. 3. A longitudinal Section of the Penis. 

m m, The corpora cavernosa penis, divided 
by o, The septum penis, n, The corpus ca- 
vernosum glandis, which is the continuation of 
that of the urethra. 




,mm ^ 









V. 







V 
^ 



. 



Of the Abdomen. 3i7 



Fig. 4. Represents the Female Organs of Ge- 
neration. 

a, That side of the uterus which is next the 
os sacrum. 1, Its fundus. 2, Its cervix, b b, 
The Fallopian or uterine tubes, which open 
into the cavity of the uterus ; — but the other 
end is open within the pelvis, and surrounded 
by c c, The fimbriae, d d, The ovaria. e, The 
os internum uteri, or mouth of the womb. 
f f, The ligamenta rotunda, which passes 
without the belly, and is fixed to the labia pu- 
dendi. g g, The cut edges of the ligamenta 
lata, which connects the uterus to the pelvis. 
h, The inside of the vagina, i, The orifice 
of the urethra, k, The clitoris surrounded by 
(1,) The praeputium. m m, The labia puden- 
di. n n, The nymphae. 

Fig. 5. Shews the Spermatic Ducts of the 
Testicle filled with Mercury. 

A, The vas deferens. B, Its beginning, 
which forms the posterior part of the epididy- 
mis. B, The middle of the epididymis, com- 
posed of serpentine ducts. D, The head or 
anterior part of the epididymis unravelled, 
e e e e, The whole ducts which compose the 
head of the epididymis unravelled, f f, The 
vasa deferentia. g g, Rete testis, h h, Some 
rectilineal ducts which send off the vasa defe- 
rentia. i i, The substance of the testicle. 



SIB Of the Thorax. 



Fig. 6. The right Testicle entire, and the 
Epididymis filled with Mercury. 

A, The beginning of the vas deferens. B, 
The vas deferens ascending towards the 
abdomen. C, The posterior part of the epididy- 
mis, named globus minor. D, The sperma- 
tic vessels inclosed in cellular substance. E, 
The body of the epididymis. E, Its head, 
named globus major! G, Its beginning from 
the testicle. H, The body of the testicle, 
inclosed in the tunica albuginea. 



PART IV. OF THE THORAX. 



THE thorax, or chest, is that cavity of 
the trunk which extends from the clavi- 
cles, or the lower part of the neck, to the dia- 
phragm, and includes the vital organs, which are 
the heart and lungs ; and likewise the trachea 
and oesophagus.— This cavity is formed by the 
ribs and vertebras of the back, covered by a 
great number of muscles, and by the common 
integuments, and anteriorly by two glandular 
bodies called the breasts. The spaces between 
the ribs are filled up by muscular fibres, which 
from their situation are called intercostal mus- 
cles. 



Of the Thorax. 3 1 9 



Sect. I. Of the Breasts. 

The breasts may be defined to be two large 
conglomerate glands, mixed with a good deal of 
adipose membrane. The glandular part is com- 
posed of an infinite number of minute arteries, 
veins, and nerves, 

The arteries are derived from two different 
trunks; one of which is called the internal, and 
the other the external, mammary artery. The 
first of these arises from the subclavian, and the 
latter from the axillary. 

The veins every where accompany the arteries 
and are distinguished by the same name. The 
nerves are chiefly from the vertebral pairs. Like 
all other conglomerate glands, the breasts are 
made up of a great many small distinct glands, 
in which the milk is secreted from the ultimate 
branches of arteries. The excretory ducts of 
these several glands gradually uniting as they 
approach the nipple, form the tubuli lactiferi, 
which are usually more than a dozen in num- 
ber, and open at its apex, but have little or no 
communication, as has been supposed, at the 
root of the nipple. These ducts, in their course 
from the glands, are surrounded by a ligamen- 
tary elastic substance, which terminates with 
them in the nipple. Both this substance, and 
the ducts which it contains, are capable of consi- 
derable extension and contraction ; but in their 
natural state are moderately corrugated, so as to 
prevent an involuntary flow of milk, unless the 
distending force be very great from the accu- 
mulation of too great a quantity. 



320 Of the Thorax. 

The whole substance of the nipple is very- 
spongy and elastic : its external surface is un- 
even, and full of small tubercles. The nipple 
is surrounded with a disk or circle of a different 
colour, called the areola ; and on the inside of 
tiie skin, under the areola, are many sebaceous 
glands, which pour out a mucus to defend the 
areola and nipple : for the skin upon these 
parts is very thin ; and the nervous papillae lying 
very bare, are much exposed to irritation. 

The breasts are formed for the secretion of 
milk, which is destined for the nourishment of 
the child for some time after its birth. This 
secretion begins to take place soon after de- 
livery, and continues to flow for many months 
in very large quantities, if the woman suckles 
her child. 

The operation of suction depends on the 
principles of the air-pump, and the flow of 
milk through the lactiferous tubes is facilitated 
by their being stretched out. 

The milk, examined chemically, appears to 
be composed of oil, mucilage, and water, and of 
a considerable quantity of sugar. The gene- 
rality of physiologists have supposed that, like 
the chyle, it frequently retains the properties 
of the aliment and medicines taken into the 
stomach ; but from some late experiments,* this 
supposition appears to be ill-founded. 

Sect. II. Of the Pleura. 

The cavity of the thorax is everywhere lined 
by a membrane of a firm texture called pleura. 
It is composed of two distinct portions or bags, 

* Jonrn. de Med. 1781. 






Of the Thorax, 321 

which, by being applied to each other laterally, 
form a septum called mediastinum ; which di- 
vides the cavity into two parts, and is attached 
posteriorly to the vertebrae of the back, and 
anteriorly to the sternum. But the two laminae 
of which this septum is formed, do not every" 
where adhere to each other ; for at the lower 
part of the thorax they are separated, to afford 
a lodgment to the heart ; and at the upper part 
of the cavity, they receive between them the 
thymus. 

The pleura is plentifully supplied with 
arteries and veins from the internal mammary 
and the intercostals. Its nerves, which are 
very inconsiderable, are derived chiefly from 
the dorsal and intercostal nerves. 

The surface of the pleura, like that of the pe- 
ritonaeum and other membranes lining cavities, 
is constantly bedewed with a serous moisture* 
which prevents adhesion of the viscera. 

The mediastinum, by dividing the breast into 
two cavities, obviates many inconveniences, to 
which we should otherwise be liable. It pre- 
vents the two lobes of the lungs from com- 
pressing each other when we lie on one side ; 
and consequently contributes to the freedom ot 
respiration, which is disturbed by the least 
pressure on the lungs. If the point of a sword 
penetrates between the ribs into the cavity of 
the thorax, the lungs on that side cease to per- 
form their office ; because the air being ad- 

S s 

* When this fluid is exhaled in too great a quantity, or is 
not properly carried off, it accumulates and constitutes the hy- 
drops pectoris. 



322 Of the Thorax. 

mitted through the wounxl, prevents the dila- 
tation of that lobe ; while the other lobe, which 
is separated from it by the mediastinum, remains 
unhurt, and continues to perform its function 
as usual. 



Sect. II. Of the Thymus. 

The thymus is a glandular substance, the 
use of which is not perfectly ascertained, its 
excretory duct not having yet been discovered. 
It is of an oblong figure, and is larger in the 
foetus and in young children than in adults, 
being sometimes nearly effaced in very old 
subjects. It is placed in the upper part of 
the thorax, between the two lamina? of the 
mediastinum ; but at first is not altogether 
contained within the cavity of the chest, being 
found to border upon the upper extremity of the 
sternum. 



Sect. IV. Of the Diaphragm. 

The cavity of the thorax is separated from 
that of the abdomen, by a fleshy and mem- 
branous substance called the diaphragm or 
midriff. The greatest part of it is composed 
of muscular fibres; and on this account sys- 
tematic writers usually place it very properly 
among the muscles. Its middle part is tendi- 
nous, and it is covered by the pleura above, 
and by the peritonaeum below. It seems to 
have been improperly named septum transver- 
sum, as it does not make a plane transverse di- 



Of the Thorax. 323 

vision of the two cavities, but forms a kind of 
vault, the fore-part of which is attached to the 
sternum. Laterally it is fixed to the last of 
the true ribs, and to all the false ribs ; and its 
lower and posterior part is attached to the 
vertebras lumborum, where it may be said to 
be divided into two portions or crura.* 

The principal arteries of the diaphragm are 
derived from the aorta, and its veins pass into 
the vena cava. Its nerves are chiefly derived 
from the cervical pairs. It affords a passage 
to the vena cava through its tendinous part, 
and to the oesophagus through its fleshy portion. 
Xhe aorta passes down behind it between its 
crura. 

The diaphragm not only serves to divide 
the thorax from the abdomen, but by its mus- 
cular structure is rendered one of the chief 
agents in respiration. When its fibres con- 
tract, its convex side, which is turned towards 
the thorax, becomes gradually flat, and by in- 
creasing the cavity of the breast, affords room 
for a complete dilatation of the lungs, by means 
of the air which is then drawn into them 
by the act of inspiration. The fibres of the di- 
aphragm then relax ; and as it resumes its for- 
mer state, the cavity of the thorax becomes gra- 
dually diminished, and the air is driven out 
again from the lungs by a motion contrary to the 
former one, called exspiration. 

* Anatomical writers have usually described the diaphragm 
as being made up of two muscles united by a middle tendon ; 
and these two portions or crura form what they speak of as the 
inferior muscle, arising from the sides and fore-part of the 
vertebras. 



324 Of the Thorax. 

It is in some measure, by means of the dia- 
phragm, that we void the faeces at the anus, and 
empty the urinary bladder. Besides these offi- 
ces, the acts of coughing, sneezing, speaking, 
laughing, gaping, and sighing, could not take 
place without its assistance ; and the gentle 
pressure which all the abdominal viscera re- 
ceive from its constant and regular motion, can- 
not fail to assist in the performance of the se- 
veral functions .which were ascribed to those 
viscera. 



Sect. V. Of the Trachea. 

The trachea or windpipe, is a cartilaginous 
and membranous canal, through which the 
air passes into the lungs. Its upper part, which 
is called the larynx, is composed of five 
cartilages. The uppermost of these cartilages 
is placed over the glottis or mouth of the 
larynx, and is called epiglottis, which has been 
before spoken of, as closing the passage to the 
lungs in the act of swallowing. At the sides 
of the glottis are placed the two arytenoide 
cartilages, which are of a very complex figure, 
not easy to be described. The anterior and 
larger part of the larynx is made up of two 
cartilages ; one of which is called thyroides or 
scutiformis, from its being shaped like a buck- 
ler ; and the other cricoides or annularis, from 
its resembling a ring. Both these cartilages 
may be felt immediately under the skin, at the 
fore-part of the throat, and the thyroides, by 
its convexity, forms an eminence called po~ 



Of the Thorax. 325 

mum adarni, which is usually more considerable 
in the male than in the female subject. 

All these cartilages are united to each other 
by means of very elastic, ligamentous fibres ; 
and are enabled by the assistance of their several 
muscles, to dilate or contract the passage of 
the larynx, and to perform that variety of 
motion which seems to point out the larynx as 
the principal organ of the voice ; for when 
the air passes out through a wound in the 
trachea, it produces no sound. 

These cartilages are moistened by a mucus 
which seems to be secreted by minute glands 
situated near them. The upper part of the 
trachea is covered anteriorly and laterally by a 
considerable body, which is supposed to be of 
a glandular structure, and from its situation 
near the thyroid cartilage is called the thyroid 
gland ; though its excretory duct has not yet 
been discovered, or its use ascertained. 

The glottis is interiorly covered by a very 
fine membrane, which is moistened by a 
constant supply of a watery fluid. From the 
larynx the canal begins to take the name of 
trachea or aspera arteria, and extends from 
thence as far down as the third or fourth verte- 
bra of the back, where it divides into two 
branches which are the right and left bron- 
chial tube. Each of these bronchi* ramifies 



* The right bronchial tube is usually found to be somewhat 
shorter and thicker than the left ; and M. Portal, who has 
published a memoir on the action of the lungs on the aorta in 
respiration, obferves that the left bronchial tube is closely 
connected by the aorta ; and trom some experiments he is 
induced to conclude, that in the first respirations the air only 
enters into the right lobe of the lungs. Mcmoins de V A.adcmu 
Royal: dss Sciences, 1769. 



326 Of the Thorax. 

through the substance of that lobe of the lungs 
to which it is distributed, by an infinite 
number of branches, which are formed of car- 
tilages separated from each other like those of 
the trachea, by an intervening membranous and 
ligamentary substance. Each of these cartilages 
is of an angular figure ; and as they become 
gradually less and less in their diameter, the 
lower ones are in some measure received into 
those above them, when the lungs, after being 
inflated, gradually collapse by the air being 
pushed out from them in exspiration. As the 
branches of the bronchi become more minute, 
their cartilages become more and more angular 
and membranous, till at length they are found 
to be perfectly membranous, and at last become 
invisible. 

The trachea is furnished with fleshy or 
muscular fibres ; some of which pass through 
its whole extent longitudinally, while the others 
are carried round it in a circular direction ; so 
that by the contraction or relaxation of these 
fibres, it is enabled to shorten or lengthen itself, 
and likewise to dilate or contract the diameter 
of its passage. 

The trachea and its branches, in all their 
ramifications, are furnished with a great num- 
ber of small glands which are lodged in their 
cellular substance, and discharge a mucous fluid 
on the inner surface of these tubes. 

The cartilages of the trachea, by keeping it 
constantly open, afford a free passage to the air 
which we are obliged to be incessantly respir- 
ing ; and its membranous part, by being capable 



Of the Thorax. 527 

of contraction and dilatation, enables us to re- 
ceive and expel the air in a greater or less quan- 
tity, and with more or less velocity, as may be 
required in singing or in declamation. This 
membranous structure of the trachea poste- 
riorly, seems likewise to assist in the descent 
of the food, by preventing that impediment to 
its passage down the oesophagus, which might 
be expected if the cartilages were complete 
rings. 

The trachea receives its arteries from the 
carotid and subclavian arteries, and its veins 
pass into the jugulars. Its nerves arise from 
the recurrent branch of the eighth pair, and 
from the cervical plexus. 

Sect. VI. Of the Lungs. 

The lungs fill the greater part of the cavity 
of the breast. They are of a soft and spongy 
texture, and are divided into two lobes, which 
are separated from each other by the me- 
diastinum, and are externally covered by a 
production of the pleura. Each of these is 
divided into two or three lesser lobes ; and we 
commonly find three in the right side of the 
cavity, and two in the left. 

To discover the structure of the lungs, it is 
required to follow the ramifications of the bron- 
chi, which were described in the last section. 
These becoming gradually more and more 
minute, at length terminate in the cellular 
spaces or vesicles, which make up the greatest 
part of the substance of the lungs, and readily 
communicate with each other. 



328 Of the Thorax. 

The lungs seem to possess but little sensibili- 
ty. Their nerves, which are small and few in 
number, are derived from the intercostal and 
eighth pair. This last pair having reached 
the thorax, sends off a branch on each side of 
the trachea, called the recurrent, which reas- 
cends at the back part of the trachea, to which 
it furnishes branches in its ascent, as well as 
to the oesophagus, but it is chiefly distributed to 
the larynx and its muscles. By dividing the 
recurrent and superior laryngeal nerves at their 
origin, an animal is deprived of its voice. 

There are two series of arteries which carry 
blood to the lungs : these are the arterise bron- 
chiales, and the pulmonary artery. 

The arterise bronchiales begin usually by 
two branches ; one of which commonly arises 
fn m the right intercostal, and the other from 
the trunk of the aorta : but sometimes there 
are three of these arteries, and in some sub- 
jects only one. The use of these arteries is to 
serve for the nourishment of the lungs, and 
their ramifications are seen creeping every 
where on the branches of the bronchi. The 
blood is brought back from them by the bron- 
chial vein into the vena azygos. 

The pulmonary artery and vein are not in- 
tended for the nourishment of the lungs ; but 
the blood in its passage through them is de- 
stined to undergo some changes, or to acquire 
certain essential properties (from the action of 
the air), which it has lost in its circulation 
through the other parts of the body. The 
pulmonary artery receives the blood from the 
right ventricle of the heart, and dividing into 



Of the Thorax. 329 

two branches, accompanies the bronchi every- 
where, by its ramifications through the lungs ; 
and the blood is afterwards conveyed back by 
the pulmonary vein, which gradually forming 
a considerable trunk, goes to empty itself into 
the left ventricle of the heart ; so that the 
quantity of blood which enters into the lungs, 
is perhaps greater than that which is sent in 
the same proportion of time through all the 
other parts of the body. 



Sect. VII. Of Respiration. 

Respiration constitutes one of those func- 
tions which are properly termed vital, as being 
essential to life ; for to live and to breathe are 
in fact synonymous terms. It consists in an 
alternate contraction and dilatation of the tho- 
rax, by first inspiring air into the lungs., and 
then expelling it from them in exspiration. 

It will perhaps be easy to distinguish and 
point out the several phenomena of respira- 
tion ; but to explain their physical cause will 
be attended with difficulty, for it will natural- 
ly be inquired, how the lungs, when emptied 
of the air, and contracted by exspiration, be- 
come again inflated, they themselves being 
perfectly passive ? How the ribs are elevated 
in opposition to their own natural situation ? 
and why the diaphragm is contracted down- 
wards towards the abdomen ? Were we to as- 
sert that the air, by forcing its way into the 
cavity of the lungs, dilated them, and conse- 
quently elevated the ribs, and pressed down 

T t 



330 Of the Thorax. 

the diaphragm, we should speak erroneously. 
What induces the first inspiration, it is not 
easy to ascertain ; but after an animal has once 
respired, it would seem likely that the blood, 
after exspiration, finding its passage through 
the lungs obstructed, becomes a stimulus, 
which induces the intercostal muscles and the 
diaphragm to contract, and enlarge the cavity 
of the thorax, in consequence perhaps of a 
certain nervous influence, which we will not 
here attempt to explain. The air then rushes 
into the lungs ; every branch of the bronchial 
tubes, and all the cellular spaces into which 
they open, become fully dilated ; and the pul- 
monary vessels being equally distended, the 
blood flows through them with ease. But as 
the stimulus which first occasioned this dilata- 
tion ceases to operate, the muscles gradually 
contract, the diaphragm rises upwards again, 
and diminishes the cavity of the chest ; the 
ribs return to their former state ; and as the 
air passes out in exspiration, the lungs gradu- 
ally collapse, and a resistance to the passage 
of the blood again takes place. But the heart 
continuing to receive and expel the blood, the 
pulmonary artery begins again to be distend- 
ed, the stimulus is renewed, and the same 
process is repeated, and continues to be re- 
peated, in a regular succession, during life : 
for though the muscles of respiration, having 
a mixed motion, are (unlike the heart) in some 
measure dependent on the will, yet no human 
being, after having once respired, can live 
many moments without it. In an attempt to 
hold one's breath, the blood soon begins to 



Of the Thorax. 331 

distend the veins, which are unable to empty 
their contents into the heart ; and we are able 
only, during a very little time, to resist the 
stimulus to inspiration. In drowning, the cir- 
culation seems to be stopped upon this prin- 
ciple ; and in hanging, the pressure made on 
the jugular veins, may co-operate with the 
stoppage of respiration in bringing on death, 

Till within these few years physiologists 
were entirely ignorant of the use of respira- 
tion. It was at length discovered in part by 
the illustrious Dr. Priestley. He found that 
the air exspired by animals was phlogistica- 
ted ; and that the air was fitter for respiration, 
or for supporting animal life, in proportion as 
it was freer from the phlogistic principle. It 
had long been observed, that the blood in pas- 
sing through the lungs acquired a more florid 
colour. He therefore suspected, that it was 
owing to its having imparted phlogiston to the 
air : and he satisfied himself of the truth of 
this idea, by experiments, which showed, that 
the eras samentum of extravasated blood., phlo- 
gisticated air in proportion as it lost its dark 
colour. He farther found, that blood thus 
reddened had a strong attraction for phlogis- 
ton ; insomuch that it was capable of taking it 
from phlogisticated air, thereby becoming of 
a darker colour. From hence it appeared that 
the blood, in its circulation through the arte- 
rial system, imbibes a considerable quantity 
of phlogiston, which is discharged from it to 
the air in the lungs. 

This discovery has since been prosecuted 
by two very ingenious physiologists, Dr. Craw* 



332 Of the Thorax. 

ford and Mr. Elliot. It had been shown by- 
professors Black and Irvine, that different bo- 
dies have different capacities for containing 
fire. For example, that oil and water, when 
equally hot to the sense and the thermometer, 
contain different proportions of that principle ; 
and that unequal quantities of it are required, 
in order to raise those substances to like tem- 
peratures. The inquiries of Dr. Crawford 
and Mr. Elliot tend to prove, that the capaci- 
ties of bodies for containing fire are diminish- 
ed by the addition of phlogiston, and increas- 
ed by its separation : the capacity of calx of 
antimony, for example, being greater than 
that of the antimony itself. Common air con- 
tains a great quantity of fire ; combustible bo- 
dies very little. In combustion, a double elec- 
tive attraction takes place ; the phlogiston of 
the body being transferred to the air, the fire 
contained in the air to the combustible body. 
But as the capacity of the latter is not increas- 
ed so much as that of the former is diminish- 
ed, only part of the extricated fire will be ab- 
sorbed by the body. The remainder there- 
fore will raise the temperature of the com- 
pound ; and hence we may account for the heat 
attending combustion. As the use of respira- 
tion is to dephlogisticate the blood, it seems 
probable, that a like double elective attraction 
takes place in this process ; the phlogiston of 
the blood being transferred to the air, and the 
fire contained in the air to the blood ; but with 
this difference, that the capacities being equal, 
the whole of the extricated fire is absorbed by 
the latter. The blood in this state circulating 



Of the Thorax. 333 

through the body, imbibes phlogiston, and of 
course gives out its fire ; part only of which is 
absorbed by the parts furnishing the phlogis- 
ton, the remainder, as in combustion, becom- 
ing sensible; and is therefore the cause of the 
heat of the body, or what is called animal 
heat. 

In confirmation of this doctrine it may be 
observed, that the venous blood contains less 
fire than the arterial ; combustible bodies less 
than incombustible ones ; and that air contains 
less of this principle, according as it is render- 
ed, by combination with phlogiston, less fit for 
respiration.* 

In ascending very high mountains, respira- 
tion is found to become short and frequent, 
and sometimes to be attended with a spitting 
of blood. These symptoms seem to be occa- 
sioned by the air being too rare and thin to 
dilate the lungs sufficiently ; and the blood 
gradually accumulating in the pulmonary ves- 
sels, sometimes bursts through their coats, and 
is brought up by coughing. This has likewise 
been accounted for in a different way, by sup- 
posing that the air contained in the blood, not 
receiving an equal pressure from that of the 
atmosphere, expands, and at length ruptures 
the very minute branches of the pulmonary 
vessels ; upon the same principle that fruits 
and animals put under the receiver of an air- 
pump, are seen to swell as the outer air be- 
comes exhausted. But Dr. Darwin of Litch- 



* See Crawford's Experiments and Observations on Animal 
Heat, and Elliot's Philosophical Observations. 



334 Of the Thorax. 

field has lately published some experiments, 
which seem to prove, that no air or elastic 
vapour does exist in the blood-vessels, as has 
been generally supposed ; and he is induced 
to impute the spitting of blood, which has 
sometimes taken place in ascending high moun- 
tains, to accident, or to violent exertions ; as 
it never happens to animals that are put into 
the exhausted receiver of an air-pump, where 
the diminution of pressure is many times 
greater than on the summit of the highest 
mountains. 



Sect. VIII. Of the Voice. 

Respiration has already been described as 
affording us many advantages ; and next to 
that of life, its most important use seems to be 
that of forming the voice and speech. The 
ancients, and almost all the moderns, have 
considered the organ of speech as a kind of 
musical instrument, which may be compared 
to a flute, to an hautboy, to an organ, &c. and 
they argue after the following manner. 

The trachea, which begins at the root of 
the tongue, and goes to terminate in the lungs, 
may be compared to the pipe of an organ, the 
lungs dilating like bellows during the time of 
inspiration ; and as the air is driven out from 
them in exspiration, it finds its passage strait- 
ened by the cartilages of the larynx, against 
which it strikes. As these cartilages are more 
or less elastic, they occasion in their turn more 
or less vibration in the air, and thus produce 



Of the Thorax. 335 

the sound of the voice ; the variation in the 
sound and tone of which depends on the state 
of the glottis, which, when straitened, pro- 
duces an acute tone, and a grave one when 
dilated. 

The late M. Ferein communicated to the 
French Academy of Sciences a very ingenious 
theory on the formation of the voice. He con- 
sidered the organ of the voice as a strings as 
well as a wind, instrument ; so that what art 
has hitherto been unable to construct, and 
what both the fathers Mersenne and Kircher 
so much wished to see, M. Ferein imagined 
he had at length discovered in the human body. 
He observes, that there are at the edges of the 
glottis certain tendinous chords, placed hori- 
zontally across it, which are capable of consi- 
derable vibration, so as to produce sound, in 
the same manner as it is produced by the 
strings of a violin or a harpsichord : and he 
supposes that the air, as it passes out from 
the lungs, acts as a bow on these strings, 
while the efforts of the breast and lungs regu- 
late its motion, and produce the variety of 
tones. So that according to this system the 
variation in the voice is not occasioned by the 
dilatation or contraction of the glottis, but by 
the distention or relaxation of these strings, 
the sound being more or less acute in propor- 
tion as they are more or less stretched out. 
Another writer on this subject supposes, that 
the organ of voice is a double instrument, 
which produces in unison two sounds of a dif- 
ferent nature ; one by means of the air, and 
the other by means of the chords of the glot- 



336 Of the Thorax. 

lis. Neither of these systems, however, arc 
universally adopted. They are both liable to 
insuperable difficulties; so that the manner in 
which the voice is formed has never yet been 
satisfactorily ascertained : we may observe, 
however, that the sound produced by the glottis 
is not articulated. To effect this, it is requir- 
ed to pass through the mouth, where it is dif- 
ferently modified by the action of the tongue, 
which is either pushed against the teeth, or 
upwards towards the palate ; detaining it in its 
passage, or permitting it to flow freely, by con- 
tracting or dilating the mouth. 



Sect. IX. Of Dejection. 

By dejection we mean the act of voiding the 
faeces at the anus ; and an account of the man- 
ner in which this is conducted was reserved 
for this part of the work, because it seemed 
to require a knowledge of respiration to be 
perfectly understood. 

The intestines were described as having a 
peristaltic motion, by which the fseces were 
gradually advancing towards the anus. Now, 
whenever the feces are accumulated in the 
intestinum rectum in a sufficient quantity to 
become troublesome, either by their weight or 
acrimony, they excite a certain uneasiness 
which induces us to go to stool. — To effect 
this, we begin by making a considerable in- 
spiration ; in consequence of which the dia- 
phragm is carried downwards towards the low- 
er belly ; the abdominal muscles are at the 



Of the Thorax. 337 

same time contracted in obedience to the will ; 
and the intestines being compressed on all 
sides, the resistance of the sphincter is over- 
come, and the faeces pass out at the anus ; 
which is afterwards drawn up by its longitu- 
dinal fibres, which are called levatores ani, and 
then by means of its sphincter is again con- 
tracted : but it sometimes happens, as in dy- 
senteries for instance, that the faeces are very 
liquid, and have considerable acrimony ; and 
then the irritation they occasion is more fre- 
quent, so as to promote their discharge with- 
out any pressure from the diaphragm or ab- 
dominal muscles ; and sometimes involuntari- 
ly, as is the case when the sphincter becomes 
paralytic. 



Sect. X. Of the Pericardium, and of the 
Heart and its Auricles. 

The two membranous bags of the pleura, 
which were described as forming the medias- 
tinum, recede one from the other, so as to af- 
ford a lodgment to a firm membranous sac, in 
which the heart is securely lodged ; this sac, 
which is the pericardium, appears to be com- 
posed of two tunics, united to each other by 
cellular membrane. — The outer coat, which 
is thick, and in some places of tendinous com- 
plexion, is a production of the mediastinum ; 
the inner coat, which is extremely thin, is re- 
flected over the auricles and ventricles of the 
heart, in the same manner as the tunica con- 

U u 



338 Of the Thorax. 

junctiva, after lining the eye-lids, is reflected 
over the eye. 

This bag adheres to the tendinous part of 
the diaphragm, and contains a coagulable 
lymph, the liquor pericardii^ which serves to 
lubricate the heart and facilitate its motions ; 
and seems to be secreted and absorbed in the 
same manner as it is in the other cavities of 
the body. 

The arteries of the pericardium are derived 
from the phrenic, and its veins pass into veins 
of the same name ; its nerves are likewise 
branches of the phrenic. 

The size of the pericardium is adapted to 
that of the heart, being usually large enough 
to contain it loosely. As its cavity does not 
extend to the sternum, the lungs cover it in 
inspiration ; and as it every where invests the 
heart, it effectually secures it from being in- 
jured by lymph, pus, or any other fluid, ex- 
travasated into the cavities of the thorax. 

The heart is a hollow muscle of a conical 
shape, situated transversely between the two 
laminae of the mediastinum, at the lower part 
of the thorax ; having its basis turned towards 
the right side, and its point or apex towards 
the left. — Its lower surface is somewhat flat- 
tened towards the diaphragm. Its basis, from 
which the great vessels originate, is covered 
with fat, and it has two hollow and fleshy ap- 
pendages, called auricles. — Round these seve- 
ral openings, the heart seems to be of a firm 
ligamentous texture, from which all its fibres 
seem to originate ; and as they advance from 



Of the Thorax. 339 

thence towards the apex, the substance of the 
heart seems to become thinner. 

The heart includes two cavities or ventricles, 
which are separated from each other by a 
fleshy septum ; one of these is called the right, 
and the other the left, ventricle ; though per- 
haps, with respect to their situation, it would 
be more proper to distinguish them into the 
anterior and posterior ventricles. 

The heart is exteriorly covered by a very 
fine membrane ; and its structure is perfectly 
muscular or fleshy, being composed of fibres 
which are described as passing in different di- 
rections ; some as being extended longitudi- 
nally from the basis to the apex ; others, as 
taking an oblique or spiral course ; and a third 
sort as being placed in a transverse direction.* 
— Within the two ventricles we observe seve- 
ral furrows ; and there are likewise tendinous 
strings, which arise from fleshy columna in the 
two cavities, and are attached to the valves of 
the auricles : That the use of these and the 
other valves of the heart may be understood, 
it must be observed, that four large vessels 
pass out from the basis of the heart, viz. two 
arteries and two veins : and that each of these 
vessels is furnished with a thin membranous 
production, which is attached all round to the 
borders of their several orifices, from whence 
hanging loosely down they appear to be divid- 
ed into two or three distinct portions. But as 

* Author* differ about the course and distinctions of these 
fibres ; and it seems right to observe, that the structure of the 
heart being more compact than that of other muscles, its fibres 
are not easily separated. 



340 Of the Thorax. 

their uses in the arteries and veins are differ- 
ent, so are they differently disposed. Those 
of the arteries are intended to give way to the 
passage of the blood into them from the ven- 
tricles, but to oppose its return : and, on the 
contrary, the valves of the veins are construct- 
ed so as to allow the blood only to pass into 
the heart. In consequence of these different 
uses, we find the valves of the pulmonary ar- 
tery and of the aorta attached to the orifices 
of those vessels, so as to have their concave 
surfaces turned towards the artery; and their 
convex surfaces, which mutually meet toge- 
ther, being placed towards the ventricle, only 
permit the blood to pass one way, which is into 
the arteries. There are usually three of these 
valves belonging to the pulmonary artery, and 
as many to the aorta ; and from their figure 
they are called valvule semilunares. The com- 
munication between the two great veins and 
the ventricles is by means of the two appen- 
dages or auricles into which the blood is dis- 
charged ; so that the other valves which may 
be said to belong to the veins, are placed in 
each ventricle, where the auricle opens into it. 
The valves in the right ventricle are usually 
three in number, and are named valvule? tri- 
cuspides ; but in the left ventricle we common- 
ly observe only two, and these are the valvule 
mitrales. The membranes which form these 
valves in each cavity are attached so as to pro- 
ject somewhat forward ; and both the tricus- 
pides and the mitrales are connected with the 
tendinous strings, which were described as 
arising from the fleshy columna. By the con- 



Of the Thorax. 341 

traction of either ventricle, the blood is driv- 
en into the artery which communicates with 
that ventricle ; and these tendinous strings 
being gradually relaxed as the sides of the ca- 
vity are brought nearer to each other, the 
valves naturally close the opening into the au- 
ricle, and the blood necessarily directs its 
course into the then only open passage, which 
is into the artery ; but after this contraction, 
the heart becomes relaxed, the tendinous 
strings are again stretched out, and, drawing 
the valves of the auricle downwards, the blood 
is poured by the veins into the ventricle, from 
whence, by another contraction, it is again 
thrown into the artery, as will be described 
hereafter. The right ventricle is not quite so 
long, though somewhat larger, than the left ; 
but the latter has more substance than the 
other: and this seems to be, because it is in- 
tended to transmit the blood to the most dis- 
tant parts of the body, whereas the right ven- 
tricle distributes it only to the lungs. 

The heart receives its nerves from the par 
vagum and the intercostals. The arteries 
which serve for its nourishment are two in 
number, and arise from the aorta. They sur- 
round in some measure the basis of the heart, 
and from this course are called the coronary 
arteries. From these arteries the blood is re- 
turned by veins of the same name into the au- 
ricles, and even into the ventricles. 

The muscular bags called the auricles are 
situated at the basis of the heart, at the sides 
of each other; and, corresponding with the 
two ventricles, are like those two cavities dis- 



342 Of the Thorax. 

tinguished into right and left. These sacs, 
which are interiorly unequal, have externally 
a jagged appendix; which, from its having 
been compared to the extremity of an ear, has 
given them their name of auricles. 



Sect. XI. Angiology, or a Description of the 
Blood-vessels. 

The heart has been described as contracting 
itself, and throwing the blood from its two ven- 
tricles into the pulmonary artery and the aor- 
ta, and then as relaxing itself and receiving a 
fresh supply from two large veins, which are 
the pulmonary vein and the vena cava. We 
will now point out the principal distributions 
of these vessels. 

The pulmonary artery arises from the right 
ventricle by a large trunk, which soon divides 
into two considerable branches, which pass to 
the right and left lobes of the lungs ; each of 
these branches is afterwards divided and sub- 
divided into an infinite number of branches and 
ramifications, which extend through the whole 
substance of the lungs ; and from these branch- 
es the blood is returned by the veins, which, 
contrary to the course of the arteries, begin 
by very minute canals, and gradually become 
larger, forming at length four large trunks 
called pulmonary veins, which terminate in the 
left auricle by one common opening, from 
whence the blood passes into the left ventricle. 
From this same ventricle arises the aorta or 
great artery, which at its beginning is nearly 



Of the Thorax. 343 

an inch in diameter ; it soon sends off two 
branches, the coronaries, which go to be dis- 
tributed to the heart and its auricles. After 
this, at or about the third or fourth vertebra 
of the back, it makes a considerable curva- 
ture ; from this curvature * arise three arte- 
ries ; one of which soon divides into two branch- 
es. The first two are the left subclavian 
and the left carotid, and the third is a com- 
mon trunk to the right subclavian and right 
carotid ; though sometimes both the carotids 
arise distinctly from the aorta. 

The two carotids ascend within the subcla- 
vian, along the sides of the trachea ; and 
when they have reached the larynx, divide 
into two principal branches, the internal and 
external carotid. The first of these runs a lit- 
tle way backwards in a bending direction ; and 
having reached the under part of the ear, pass- 
es through the canal into the os petrosum, 
and entering into the cavity of the cranium, is 
distributed to the brain and the membranes 
which envelope it, and likewise to the eye. 
The external carotid divides into several 
branches, which are distributed to the larynx, 
pharynx, and other parts of the neck ; and to 
the jaws, lips, tongue, eyes, temples, and all 
the external parts of the head. 



* Anatomists usually call the upper part of this curvature 
aorta ascendem ; and the other part of the artery to its division at 
the iliacs, aorta dcsctndens : but they differ about the place where 
this distinction is to be introduced ; and it seems sufficiently to 
answer every purpose, to speak only of the aorta and its curva- 
ture. 



344 Of the Thorax. 

Each subclavian is likewise divided into a 
great number of branches. It sends off the 
vertebral artery, which passes through the 
openings we see at the bottom of the transverse 
processes of the vertebrae of the neck, and in 
its course sends off many ramifications to the 
neighbouring parts. Some of its branches are 
distributed to the spinal marrow, and after a 
considerable inflection it enters into the crani- 
um, and is distributed to the brain. The sub- 
clavian likewise sends off branches to the mus- 
cles of the neck and scapula; and the medias- 
tinum, thymus, pericardium, diaphragm, the 
breasts, and the muscles of the thorax, and 
even of the abdomen, derive branches from 
the subclavian, which are distinguished by 
different names, alluding to the parts to which 
they are distributed; as the mammary, the 
phrenic, the intercostal, &c. But notwithstand- 
ing the great number of branches which have 
been described as arising from the subclavian, 
it is still a considerable artery when it reach- 
es the axilla, where it drops its former name, 
which alludes to its passage under the clavi- 
cle, and is called the axillary artery ; from 
which a variety of branches are distributed to 
the muscles of the breast, scapula, and arm. — 
But its main trunk taking the name of brachi- 
alis, runs along on the inside of the arm near 
the os humeri, till it reaches the joint of the 
fore-arm, and then it divides into two branch- 
es. This division however is different in dif- 
ferent subjects ; for in some it takes place high- 
er up and in ethers lower down. When it 
happens to divide above the joint, it may be 



Of the Thorax. 345 

considered as a happy disposition in case of an 
accident by bleeding ; for supposing the artery 
to be unfortunately punctured by the lancet, 
and that the haemorrhage could only be stop- 
ped by making a ligature on the vessel, one 
branch would remain unhurt, through which 
the blood would pass uninterrupted to the fore- 
arm and hand. One of the two branches of 
the brachialis plunges down under the flexor 
muscles, and runs along the edge of the ulna ; 
while the other is carried along the outer sur- 
face of the radius, and is easily felt at the 
wrist, where it is only covered by the common 
integuments. Both these branches commonly 
unite in the palm of the hand, and form an ar- 
terial arch from whence branches are detached 
to the fingers. 

The aorta, after having given off at its cur- 
vature the carotids and subclavians which con- 
vey blood to all the upper parts of the body, 
descends upon the bocjies of the vertebrae a lit- 
tle to the left, as far as the os sacrum, where 
it drops the name of aorta, and divides into 
two considerable branches. In this course, 
from its curvature to its bifurcation, it sends 
off several arteries in the following order : 1. 
One or two little arteries, first demonstrated 
by Ruysch as going to the bronchi, and called 
arterue brondiinales Ruyschii. 2. The arteriae 
oesophageal. These are commonly three or 
four in number. They arise from the fore- 
part of the aorta, and are distributed chiefly to 
the oesophagus. 3. The inferior intercostal 
arteries, which are distributed between the 
ribs in the same manner as the arteries of the 

X x 



346 Of the Thorax. 

three or four superior ribs are, which are de- 
rived from the subclavian. These arteries 
send off branches to the medulla spinalis. 4, 
The diaphragmatic or inferior phrenic arteries, 
which go to the diaphragm, stomach, omentum, 
duodenum, pancreas, spleen, liver, and 'gall- 
bladder. 5. The cceliac, which sends off the 
coronary-stomachic, the splenic, and the hepa- 
tic artery. 6. The superior mesenteric artery, 
which is distributed to the mesentery and small 
intestines, 7. The emulgents, which go to the 
kidneys. 8. The arteries, which are distri- 
buted to the glandulse renales. 9. The sper- 
matic. 10. The inferior mesenteric artery, 
which ramifies through the lower portion of the 
mesentery and the large intestines. — A branch 
of this artery which goes to the rectum is call* 
ed the internal hemorrhoidal. 11. The lum- 
bar arteries, and a very small branch called 
the sacra, which are distributed to the mus- 
cles of the loins and abdomen, and to the os 
sacrum and medulla spinalis. 

The trunk of the aorta, when it has reached 
the last vertebra lumborum, or the os sacrum, 
drops the name of aorta, and separates into two 
forked branches called the iliacs. Each of 
these soon divides into two branches ; one of 
which is called the internal iliac, or hypogas- 
tric artery, and is distributed upon the contents 
of the pelvis and upon the muscles on its out- 
er side. One branch, called pudenda commu- 
nis, sends small ramifications to the end of 
the rectum under the name of hamorrhoidales 
externa, and is afterwards distributed upon 
the penis. The other branch, the external ili- 



Of the Thorax. 347 

ac, after having given off the circumflex artery 
of the os ilium and the epigastric, which is 
distributed to the recti-muscles, passes out of 
the abdomen under Poupart's ligament, and 
takes the name of crural artery. It descends 
on the inner part of the thigh close to the os 
femoris, sending off branches to the muscles, 
and then sinking deeper in the hind part of 
the thigh, reaches the ham, where it takes 
the name of popliteal : after this it separates into 
two considerable branches ; one of which is 
called the anterior tibial artery ; the other di- 
vides into two branches, and these arteries all 
go to be distributed to the leg and foot. 

The blood, which is thus distributed by the 
aorta to all parts of the body, is brought back 
by the veins, which are supposed to be conti- 
nued from the ultimate branches of arteries ; 
and uniting together as they approach the 
heart, at length form the large trunks, the ve- 
na cava ascendens, and vena cava descendens. 

All the veins which bring back the blood 
from the upper extremities, and from the head 
and breast, pass into the vena cava descendens ; 
and those which return it from the lower parts 
of the body terminate in the vena cava ascen- 
dens.; and these two eavas uniting together as 
they approach the heart, open by one common 
orifice into the left auricle. 

It does not here seem to be necessary to fol- 
low the different divisions of the veins as we 
did those of the arteries ; and it will be suffi- 
cient to remark, that in general every artery is 
accompanied by its vein, and that both are dis- 
tinguished by the same name. But, like many 



548 Of the Thorax. 

other general rules, this too has its excep- 
tions.* The veins for instance, which accom- 
pany the external and internal carotid, are not 
called the carotid veins, but the external and in- 
ternal jugular. — In the thorax, there is a vein 
distinguished by a proper name, and this is the 
azygos, or vena sine pari. This vein, which 
is a pretty considerable one, runs along by the 
right side of the vertebrae of the back, and is 
chiefly destined to receive the blood from the 
intercostals on that side, and from the lower 
half of those on the left side, and to convey it 
into the vena cava descendens. In the abdo- 
men we meet with a vein, which is still a more 
remarkable one, and this is the vena porta?, 
which performs the office both of an artery and 
a vein. It is formed by a re-union of all the 
veins which come from the stomach, intestines, 
omentum, pancreas, and spleen, so as to com- 
pose one great trunk, which goes to ramify 
through the liver ; and after having deposited 
the bile, its ramifications unite and bring back 
into the vena cava, not only the blood which 
the vena portae had carried into the liver, but 
likewise the blood from the hepatic artery. 
Every artery has a vein which corresponds with 
it ; but the trunks and branches of the veins 
are more numerous than those of the arteries. 
— The reasons for this disposition are perhaps 
more difficult to be explained ; the blood in its 
course through the veins is much farther re- 
moved from the source and cause of its mo- 

* In the extremities, some of the deep-seated veins, and all 
the superficial ones, take a course different from that of the 
arteries. 



^ Of the Thorax. 349 

tion, which are in the heart, than it was when 
in the arteries ; so that its course is consequent' 
ly less rapid, and enough of it could not pos- 
sibly be brought back to the heart in the mo- 
ment of its dilatation, to equal the quantity 
which is driven into the arteries from the two 
ventricles, at the time they contract ; and the 
equilibrium which is so essential to the conti- 
nuance of life and health would consequently 
be destroyed, if the capacity of the veins did 
not exceed that of the arteries, in the same pro- 
portion that the rapidity of the blood's motion 
through the arteries exceeds that of its return 
through the veins. 

A large artery ramifying through the body, 
and continued to the minute branches of veins, 
which gradually unite together to form a large 
trunk, may be compared to two trees united to 
each other at their tops ; or rather as having 
their ramifications so disposed that the two 
trunks terminate in one common point; and if we 
farther suppose, that both these trunks and their 
branches are hollow, and that a fluid is inces- 
santly circulated through them, by entering in- 
to one of the trunks and returning through the 
other, we shall be enabled to conceive how the 
blood is circulated through the vessels of the 
human body. 

Every trunk of an artery, before it divides, 
is nearly cylindrical, or of equal diameter 
through its whole length, and so are all its 
Jbranches when examined separately. But eve- 
ry trunk seems to contain less blood than the 
many branches do into which that trunk sepa- 
rates ; and each of these branches probably 



350 Of the Thorax. . 

contains less blood than the ramifications do 
into which it is subdivided : and it is the same 
with the veins ; the volume of their several 
ramifications, when considered together, being 
found to exceed that of the great trunk which 
they form by their union. 

The return of the blood through the veins 
to the heart, is promoted by the action of the 
muscles, and the pulsation of the arteries. 
And this return is likewise greatly assisted by 
the valves which are to be met with in the 
veins, and which constitute one of the great 
distinctions between them and the arteries. 
These valves, which are supposed to be form- 
ed by the inner coat of the veins, permit the 
blood to flow from the extremities towards the 
heart, but oppose its return. They are most 
frequent in the smaller veins. As the column 
of blood increases, they seem to become less 
necessary ; and therefore in the vena cava as- 
cendens, we meet with only one valve, which 
is near its origin. 

The arteries are composed of several tunics. 
Some writers enumerate five of these tunics ; 
but perhaps we may more properly reckon only 
three, viz. the nervous, muscular, and cuticular 
coats. The veins are by some anatomists de- 
scribed as having the same number of coats as 
the arteries ; but as they do not seem to be ir- 
ritable, we cannot with propriety suppose them 
to have a muscular tunic. We are aware of 
Dr. Verschuir's* experiments to prove that 
the jugular and some other veins possess a 

* De Arteriarum et Venarum vi irritabili, 4to. 



Of the Thorax. 351 

certain degree of irritability; but it is cer- 
tain, that his experiments, repeated by others, 
have produced a different result ; and even he 
himself allows, that sometimes he was unable 
to distinguish any such property in the veins. 
Both these series of vessels are nourished by 
still more minute arteries and veins, which are 
seen creeping over their coats, and ramifying 
through their whole substance, and are called 
vasa vasorum : they have likewise many mi- 
nute branches of nerves. 

The arteries are much stronger than the 
veins, and they seem to require this force to 
be enabled to resist the impetus with which the 
blood circulates through them, and to impel it 
on towards the veins. 

When the heart contracts, it impels the blood 
into the arteries, and sensibly distends them ; 
and these vessels again contract, as the heart 
becomes relaxed to receive more blood from 
the auricles ; so that the cause of the contrac- 
tion and dilatation of the arteries seems to be 
easy to be understood, being owing in part to 
their own contractile power, and in part to the 
action of the heart ; but in the vei?is, the effects 
of this impulse not being so sensibly felt, and 
the vessels themselves having little or no con- 
tractile power, the blood seems to flow in a 
constant and equal stream : and this, together 
with its passing gradually from a small channel 
into a larger one, seems to be the reason why 
the veins have no pulsatory motion, except the 
large ones near the heart ; and in these it seems 
to be occasioned by the motion of the dia- 
phragm, and by the regurgitation of the blood 
in the cavas. 



52 Of the Thorax. 



Sect. XII. Of the Action of the Heart, 
Auricles, and Arteries. 

The heart, at the time it contracts, drives 
the blood from its ventricles into the arteries ; 
and the arteries being thus filled and distended, 
are naturally inclined to contract the moment 
the heart begins to dilate, and ceases to supply 
them with blood. These alternate motions of 
contraction and dilatation of the heart and ar- 
teries, are distinguished by the names of systole 
and diastole. When the heart is in a state of 
contraction or systole, the arteries are at that 
instant distended with blood, and in their 
diastole ; and it is in this state we feel their 
pulsatory motion which we call the pulse. 
When the heart dilates, and the arteries contract, 
the blood is impelled onwards into the veins 
through which it is returned back to the heart. 
While the heart, however, is in its systole, the 
blood cannot pass from the veins into the 
ventricles, but is detained in the auricles, which 
are two reservoirs formed for this use, till the 
diastole, or dilatation of the heart, takes place ; 
and then the distended auricles contract, and 
drive the blood into the ventricles ; so that the 
auricles have an alternate systole and diastole 
as well as the heart. 

Although both the ventricles of the heart 
contract at the same time, yet the blood pass- 
es from one to the other. In the same mo- 
ment, for instance, that the left ventricle 
drives the blood into the aorta, the right ven- 
tricle impels it into the pulmonary artery. 



Of the Thorax. 353 

which is distributed through all the substance 
of the lungs. The blood is afterwards brought 
back into the left ventricle by the pulmonary 
vein, at the same time that the blood is returned 
by the cavas, into the right ventricle, from all 
the other parts of the body. 

This seems to be the mode of action of the 
heart and its vessels ; but the cause of this action 
has, like all other intricate and interesting sub- 
jects, been differently explained. It seems to 
depend on the stimulus made on the different 
parts of the heart by the blood itself, which by 
its quantity and heat, or other properties,* is 
perhaps capable of first exciting that motion, 
which is afterwards continued through life, in- 
dependent of the will, by a regular return of 
blood to the auricles, in a quantity proportion- 
ed to that which is thrown into the arteries. 

The heart possesses the vis insita, or prin- 
ciple of irritability, in a much greater degree 
than any other muscle of the body. The pulse 
is quicker in young than in old subjects, be- 
cause the former are cat. par. more irritable 
than the latter. Upon the same principle we 
may explain, why the pulse is constantly quick- 
er in weak than in robust persons. 
Y y 

* Dr. Harvey long ago suggested, that the blood is possessed 
of a living principle ; and Mr. J. Hunter has lately endeavoured 
to revive this doctrine : in support of which he has adduced many 
ingenious arguments. The subject is a curious one, and deferves 
to he prosecuted as an inquiry which cannot but be interesting 
to physiologists. 



354 Of the Thorax. 



Sect. XIII. Of the Circulation. 

After what has been observed of the 
structure and action of the heart and its 
auricles, and likewise of the arteries and veins r 
there seem to be but very few arguments 
required to demonstrate the circulation of the 
blood, which has long since been established 
as a medical truth. This circulation may be 
defined to be a perpetual motion of the blood, 
in consequence of the action of the heart and 
arteries, which impel it through all the parts 
of the body, from whence it is brought back 
by the veins of the heart. 

A very satisfactory proof of this circulation, 
and a proof easy to be understood, may be de- 
duced from the different effects of pressure on 
an artery and a vein. If a ligature, for instance, 
is passed round an artery, the vessel swells 
considerably between the ligature and the 
heart ; whereas if we tie up a vein, it only be- 
comes filled between the extremity and the 
ligature, and this is what we every day observe 
in bleeding. The ligature we pass round the 
arm on these occasions, compresses the super- 
ficial veins; and the return of the blood 
through them being impeded, they become dis- 
tended. When the ligature is too loose, the 
veins are not sufficiently compressed, and the 
blood continues its progress towards the heart ; 
and, on the contrary, when it is made too tight, 
the arteries themselves become compressed; 



Of the Thorax. 355 

and the flow of the blood through them being 
impeded, the veins cannot be distended. 

Another phenomenon, which effectually 
proves the circulation, is the loss of blood that 
every living animal sustains by opening only 
a single artery of a moderate size ; for it con- 
tinues to flow from the wounded vessel till the 
equilibrium is destroyed which is essential to 
life. This truth was not unknown to the an- 
cients ; and it seems strange that it did not 
lead them to a knowledge of the circulation, as 
it sufficiently proves, that all the other vessels 
must communicate with that which is opened. 
Galen, who lived more than 1500 years ago, 
drew this conclusion from it ; and if we far- 
ther observe, that he describes (after Erasis- 
tratus, who flourished about 450 years before 
him) the several valves of the heart, and de- 
termines their disposition and uses, it will ap- 
pear wonderful, that a period of near 2Q00 
years should afterwards elapse before the true 
course of the blood was ascertained. This 
discovery, for which we are indebted to the 
immortal Harvey, has thrown new lights on 
physiology and the doctrine of diseases, and 
constitutes one of the most important periods 
of anatomical history. 



Sect. XIV. Of the Nature of the Blood. 

Blood, recently drawn from a vein into a 
bason, would seem to be an homogeneous fluid 



356 Of the Thorax. 

of a red colour ;* but when suffered to rest, it 
Soon coagulaies, and divides into two parts, 
which are distinguished by the names of cras- 
samentum and scrum. The crassamentum is 
the red coagulum, and the serum is the water 
in which it floats. Each of these may be again 
separated into two others ; for the crassamen- 
tum, by being repeatedly washed in warm wa- 
ter, gives out all its red globules, and what 
remains appears to be composed of the coagu- 
lable lymph,f which is a gelatinous substance, 
capable of being hardened by fire till it becomes 
p. rfectly horny : and if we expose the serum 
to a certain degree of heat, part of it will be 
found to coagulate like the white of an egg, 
and there will remain a clear and limpid water, 
resembling urine both in its appearance and 
smell. 

The serum and crassamentum differ in 
their proportion in different constitutions ; in 
a strong person, the crassamentum is in a great- 
er proportion to the serum than in a weak 
one ;J and the same difference is found to take 
place in diseases. J 

* The blood, as it flows through the arteries, is observed to 
be more florid than it is in the veins ; and this redness is acquir- 
ed in its passage through the lungs. Fid. feet. vii. 

f It may not be improper to observe, that till of late the coa- 
gulable lymph has been confounded with the strum of the % blood, 
which contains a substance that is likewise coagulable, though 
only when exposed to heat, or combined with certain chemical 
substances; whereas the other coagulates spontaneously when 
exposed t'> the air or to rest. 

\ Hewson's Experim. Enq. Part I. 

§ When the blood separates into strum and crassamentum, if the 
latter be covered with a crust of a whitish or buff colour, it has 
been usually considered as a certain proof of the blood's being in 
a state of too great viscidity. This appearance commonly taking 
place in inflammatory diseases, has long served to confirm the 



Of the Thorax. 35' 



Sect. XV. Of Nutrition. 

The variety of functions which we have de- 
scribed as being incessantly performed by the 
living body, and the continual circulation of the 
blood through it, must necessarily occasion a 
constant dissipation of the several parts which 
enter into its composition. In speaking of the 
insensible perspiration, we observed how much 
was incessantly passing off from the lungs and 
the surface of the skin. The discharge by 
urine is likewise every day considerable ; and 
great part of the bile, saliva, he. are excluded 
by stool. But the solid, as well as the fluid 
parts of the body, require a constant renewal 
of nutritious particles. They are exposed to 
the attrition of the fluids which are circulated 
through them ; and the contraction and relax- 
ation they repeat so many thousand times in 
every day, would necessarily occasion a disso- 
lution of the machine, if the renewal was not 
proportioned to the waste. 

It is easy to conceive how the chyle formed 
from the aliment is assimilated into the nature 

theory which ascribes the cause of inflammation to lentor and ob- 
structions. But from the late Mr. Hewson's experiments it ap- 
pears, that when die action of the arteries is increased, the blood, 
instead of being more viscid, is, on the contrary, more fluid than 
in the ordinary state, previous to inflammation ; and that in con- 
sequence of this, the coagulable lymph suffers the red globules, 
which arc the heaviest part of the blood, to fall down to the bot- 
tom before it coagulates ; so that the crassamentum is divided 
into two parts : one of which is found to consist of the coagula- 
ble lymph alone (in this case termed the bvjf) ; and the other, 
partly of this and partly of the red globules. 



358 Of the Thorax. 

of blood, and repairs die loss of the fluid parts 
of our body ; but how the solids are renewed, 
has never yet been satisfactorily explained. 
The nutritious parts of the blood are probably 
deposited by the arteries by exsudation through 
their pores into the tela cellulosa ; and as the 
solid parts of the body are in the embryo only 
a kind of jelly, which gradually acquires the 
degree of consistence they are found to hove 
when the body arrives at a more advanced 
age ; and these same parts which consist of 
bones, cartilages, ligaments, muscles, &c. are 
sometimes reduced again by disease to a gela- 
tinous state ; we may, with some degree of 
probability, consider the coagulable lymph as 
the source of nutrition. 

If the supply of nourishment exceeds the 
degree of waste, the body increases; and this 
happens in infancy and in youth : for at those 
periods, but more particularly the former one, 
the fluids bear a large proportion to the solids ; 
and the fibres being soft and yielding, are pro- 
portionably more capable of extension and in- 
crease. But when the supply of nutrition only 
equals the waste, we neither increase nor de- 
crease; and we find this to be the case when 
the body has attained its full growth or acme : 
for the solids having then acquired a certain 
degree of firmness and rigidity, do not permit 
a farther increase of the body. But as we ap- 
proach to old age, rigidity begins to be in ex- 
cess, and the fluids * bear a much less propor- 

* As the fluids become less in proportion to the solids, their 
acrimony is found to increase ; ;md this may perhaps compen- 
sate for the want of fluidity in the blood by diminishing its co- 
hesion. 



Of the Thorax. 3 59 

tion to the solids than before. The dissipation 
of the body is greater than the supply of nour- 
ishment ; many of the smaller vessels become 
gradually impervious ;* and the fibres losing 
their moisture and their elasticity, appear flac- 
cid and wrinkled. The lilies and the roses dis- 
appear, because the fluids by which they were 
produced can no longer reach the extremities 
of the capillary vessels of the skin. As these 
changes take place, the nervous power being 
proportionably weakened, the irritability and 
sensibility of the body, which were formerly 
so remarkable, are greatly diminished ; and in 
advanced life, the hearing, the eye-sight, and 
all the other senses, become gradually im- 
paired. 

Sect. XVI. Of the Glands and Secretions, 

The glands are commonly understood to be 
small, roundish, or oval bodies formed by the 
convolution of a great number of vessels, and 
destined to separate particular humours from 
the mass of blood. 

They are usually divided into two classes ; 
but it seems more proper to distinguish three 
kinds of glands, viz. the mucous, conglobate, 
and conglomerate. 

The mucous glands, or follicles, as they are 
most commonly called, are small cylindrical 

* In infancy, the arteries are numerous and large in respect 
to the veins, and the lymphatic glands are larger than at any 
other time of life ; whereas, in old age, the capacity of the ve- 
nous system exceeds that of the arteries and the lymphatic sys- 
tem almost disappears. 



360 Of the Thorax. 

tubes continued from the ends of arteries. In 
some parts of the body, as in the tonsils, for 
example, several of these follicles may be seen 
folded together in one common covering, and 
opening into one common sinus. These folli- 
cles are the vessels that secrete and pour out 
mucus in the mouth, oesophagus, stomach, in- 
testines, and other parts of the body. 

The conglobate glands are peculiar to the 
lymphatic system. Every lymphatic vein pass- 
es through a gland of this kind in its way to 
the thoracic duct. They are met with in dif- 
ferent parts of the body, particularly in the 
axilla, groin, and mesentery, and are either 
solitary or in distinct clusters. 

The conglomerate glands are of much great- 
er bulk than the conglobate, and seem to be an 
assemblage of many smaller glands. Of this 
kind are the liver, kidneys, See. Some of them, 
as the pancreas, parotids, &tc. have a granu- 
lated appearance. All these conglomerate 
glands are plentifully supplied with blood-ves- 
sels ; but their nerves are in general very mi- 
nute, and few in number. Each little granu- 
lated portion furnishes a small tube, which 
unites with other similar ducts, to form the 
common excretory duct of the gland. 

The principal glands, and the humours 
they secrete, have been already described in 
different parts of this work; and there only 
remains for us to examine the general structure 
of the glands, and to explain the mechanism 
of secretion. On the first of these subjects 
two different systems have been formed ; each 
of which has had, and still continues to have, 



Of the Thorax. 361 

its adherents. One of these systems was ad- 
vanced by Malpighi, who supposed that an ar- 
tery entering into a gland ramifies very mi- 
nutely through its whole substance ; and that 
its branches ultimately terminate in a vesicu- 
lar cavity or follicle, from whence the secreted 
fluid passes out through the excretory duct. 
This doctrine at first met with few opponents ; 
but the celebrated Ruysch, who first attempt- 
ed minute injections with wax, afterwards dis- 
puted the existence of these follicles, and as- 
serted, that every gland appears to be a con- 
tinued series of vessels, which after being re- 
peatedly convoluted in their course through 
its substance, at length terminate in the ex- 
cretory duct. Anatomists are still divided be- 
tween these two systems: that of Malpighi, 
however, seems to be the best founded. 

The mode of secretion has been explained 
in a variety of ways, and they are all perfectly 
hypothetical. In such an inquiry it is natural 
to ask, how one gland constantly separates a 
particular humour, while another gland se- 
cretes one of a very different nature from the 
blood ? The bile, for instance, is separated 
by the liver, and the urine by the kidneys- Are 
these secretions to be imputed to any particu- 
lar dispositions in the fluids, or is their cause 
to be looked for in the solids ? 

It has been supposed, that every gland con- 
tains within itself a fermenting principle, by 
which it is enabled to change the nature of the 
blood it receives, and to endue it with a par- 
ticular property. So that, according to this 
system, the blood, as it circulates through the 

Z z 



362 Of the Thorax. 

kidneys, becomes mixed with the fermenting 
principle of those glands, and a part of it is 
converted into urine ; and again, in the liver, 
in the saiival and other glands, the bile, the 
saliva, and other juices, are generated from a 
similar cause. But it seems to be impossible 
for any liquor to be confined in a place expos- 
ed to the circulation, without being carried 
away by the torrent of blood, every part of 
which would be equally affected ; and this sys- 
tem of fermentation has long been rejected as 
vague and chimerical. But as the cause of se- 
cretion continued to be looked for in the fluids, 
the former system was succeeded by another, 
in which recourse was had to the analogy of 
the humours. It was observed, that if paper 
is moistened with water, and oil and water are 
afterwards poured upon it, that the water only 
will be permitted to pass through it; but that, 
on the other hand, if the paper has been pre- 
viously soaked in oil instead of water, the oil 
only, and not the water will be filtered through 
it. These observations led to a supposition, 
that every secretory organ is originally furnish- 
ed with a humour analogous to that which it is 
afterwards destined to separate from the blood ; 
and that in consequence of this disposition, the 
secretory vessels of the liver, for instance, will 
only admit the bilious particles of the blood, 
while all the other humours will be excluded. 
This system is an ingenious one, but the dif- 
ficulties with which it abounds are unanswer- 
able ; for oil and water are immiscible ; where- 
as the blood, as it is circulated through the 
body, appears to be an homogeneous fluid. 



Of the Thorax, 363 

Every oil will pass through a paper moistened 
only with one kind of oil ; and wine, or spirits 
mixed with water, will easily be filtered through 
a paper previously soaked in water. Upon 
the same principle, all our humours, though 
differing in their other properties, yet agree- 
ing in that of being perfectly miscible with 
each other, will all easily pass through the 
same nitre. — But these are not all the objec- 
tions to this system. The humours which are 
supposed to be placed in the secretory vessels 
for the determination of similar particles of the 
blood, must be originally separated without 
any analogous fluid ; and that which happens 
once, may as easily happen always. Again, 
it sometimes happens from a vicious disposi- 
tion, that humours are filtered through glands 
which are naturally not intended to afford 
them a passage, and when this once has hap- 
pened, it ought, according to this system, to 
be expected always to do so : whereas this is 
not the case; and we are, after all, naturally 
led to seek for the cause of secretions in the 
solids. It does not seem right to ascribe it to 
any particular figure of the secretory vessels ; 
because the soft texture of those parts does 
not permit them to preserve any constant 
shape, and our fluids seem to be capable of 
accommodating themselves to every kind of 
figure. Some have imputed it to the differ- 
ence of diameter in the orifices of the differ- 
ent secretory vessels. To this doctrine ob- 
jections have likewise been raised; and it has 
been argued, that the vessels of the liver, for 
instance, would, upon this principle, ailord a 



3(54 Of the Thorax. 

passage not only to the bile, but to all the 
other humours of less consistence with it. In 
reply to this objection, it has been supposed, 
that secondary vessels exist, which originate 
from the first, and permit all the humours 
thinner than the bile to pass through them. 

Each of these hypotheses is probably very 
remote from the truth. 



EXPLANATION of PLATE XXVIII. 

This plate represents the Heart in situ, all 
the large Arteries and Veins, with some of the 
Muscles, &c. 

Muscles, &c. — Superior Extremity. — a> 
Masseter. b, Complexus. c, Digastricus. d, 
Os hyoides. e, Thyroid gland, f, Levator 
scapulas, g, Cucullaris. h h, The clavicles 
cut. i, The deltoid muscle, k, Biceps flexor 
cubiti cut. 1, Caraco-brachialis. m, Triceps 
extensor cubiti. n, The heads of the pronator 
teres, flexor carpi radialis, and flexor digito- 
rum sublimis, cat. o, The flexor carpi ulna- 
ris, cut at its extremity, p, Flexor digitorum 
profundus, q, Supinator radii longus, cut at 
its extremity, r, Ligamentum carpi transver- 
sale. s, Extensores carpi radiales. t, Latis- 
simus dorsi. u, Anterior edge of the serratus 
anticus major, v v, The inferior part of the 
diaphragm, w w, Its anterior edge cut. x x, 
The kidneys, y, Transversus abdominis, z, 
Os ilium. 







B 



Of the Thorax. 365 

Inferior Extremity. — «, Psoas magnus, 
b, Iliacus internus. r, The fleshy origin of the 
tensor vaginae femoris. d ch The ossa pubis 
cut from each other. <?, Musculus pectineus 
cut from its origin. /, Short head of the tri- 
ceps abductor femoris cut. g, The great head 
of the triceps, h, The long head cut. i, Vas- 
tus internus. k, Vastus externus. /, Crure- 
us. m, Gemellus, n, Soleus. o, Tibia, fa 
Peronaeus longus. q, Peronaeus brevis. r ? 
Fibula. 

Heart and Blood-vessels. — A, The heart, 
with the coronary arteries and veins. B, The 
right auricle of the heart. C, The aorta ascen- 
dens. D, The left subclavian artery. E, The 
left carotid artery. E, The common trunk 
which sends off the right subclavian and right 
carotid arteries. G, The carotis externa. H, 
Arteria facialis, which sends off the coronary 
arteries of the lips. I, Arteria temporalis pro- 
funda. K, Aorta descendens. L L, The 
iliac arteries, — which send off M M, The fe- 
moral or crural arteries. jV. B. The other 
arteries in this figure have the same distri- 
bution as the veins of the same name : — 
And generally, in the anatomical plates, the 
description to be found on the one side, points 
out the same parts in the other. 1, The fron- 
tal vein. 2, The facial vein. 3, Vena tem- 
poralis profunda. 4, Vena occipitalis. 5, 
Vena jngularis externa. 6, Vena jugularis 
interna, covering the arteria carotis commu- 
nis. 7. The vascular arch on the palm of the 
hand, which is formed by, 8, The radial ar- 
tery and vein, and, 9, The ulnar artery and 



366 Of the Brain and Nerves. 

vein. 10 10, Cephalic vein. 11, Basilic vein, 
that on the right side cut. 12, Median vein. 
13, The humeral vein, which, with the me- 
dian, covers the humeral artery. 14 14, The 
external thoracic or mammary arteries and 
veins. 15, The axillary vein, covering the 
artery. 16 16, The subclavian veins, which, 
Avith (6 6) the jugulars, form, 17, The vena 
cava superior. 18, The cutaneous arch of 
veins on the fore part of the foot. 19, The 
vena tibialis antica, covering the artery. 20, 
The vena profunda femoris, covering the ar- 
tery, 21, The upper part of the vena saphena 
major. 22, The femoral vein. 23 23, The 
iliac veins. 24 24, Vena cava inferior. 25 25, 
The renal veins covering the arteries. 26 26, 
The diaphragmatic veins. 



PART V. OF THE BRAIN AND 
NERVES. 



Sect. I. Of the Brain and its Integuments. 

THE bones of the cranium were described 
in the osteological part of this work, as 
inclosing the brain, and defending it from ex- 
ternal injury : but they are not its only pro- 
tection ; for when we make an horizontal sec- 
tion through these bones, we find this mass 



Of the Brain and Nerves. 367 

every whejre surrounded by two membranes,* 
the dura and pia mater. — The first of these 
lines the interior surface of the cranium, to 
which it every where adheres strongly,! but 
more particularly at the sutures, and at the 
many foramina through which vessels pass 
between it and the pericranium. The dura 
mater i is perfectly smooth and inelastic, and 
its inner surface is constantly bedewed with a 
fine pellucid fluid, which every where sepa- 
rates it from the pia mater. The dura mater 
sends off several considerable processes, which 
divide the brain into separate portions, and 
prevent them from compressing each other. 
Of these processes there is one superior and 
longitudinal, called the falx or falciform pro- 
cess, from its resemblance to a scythe. It 
arises from the spine of the os frontis, near 
the crista galli, and extending along in the 
direction of the sagittal suture, to beyond the 
lambdoidal suture, divides the brain into two 
hemispheres. A little below the lambdoidal 

* The Greeks called these membranes meninges ; but the Ara- 
bians, supposing them to be the source of all the other mem- 
branes of the body, afterwards gave them the names of dura and 
pia mater ; by which they are now usually distinguished. 

■j- In young subjects this adhesion is greater than in adults ; 
but even then, in the healthy subject, it is no where easily sepa- 
rable, without breaking through some of the minute vessels by 
means of which it is attached to the bone. 

\ This membrane is commonly described as consisting of two 
lamina; ; of which the external one is supposed to perform the of- 
fice of periosteum internum to the cranium, while the internal 
one forms the folds and processes of the dura mater. In the na- 
tural state, however, no such separation is apparent ; like other 
membranes, we may indeed divide it, not into two only, but 
manv lamina ; but this division is artificial, and depends on the 
dexterity of the anatomist. 



368 Of the Brain and Nerves. 

suture, it divides into two broad wings or ex- 
pansions called the transverse or lateral process- 
es, which prevents the lobes of the cerebrum, 
from pressing on the cerebellum. Besides 
these there is a fourth, which is situated under 
the transverse processes, and being continued 
to the spine of the occiput, divides the cere- 
bellum into two lobes. 

The blood, after being distributed through 
the cavity of the cranium by means of the ar- 
teries, is returned, as in the other parts of the 
body, by veins which all pass on to certain 
channels, situated behind these several pro- 
cesses. 

These canals or sinuses communicate with 
each other, and empty themselves into the in- 
ternal jugular veins, which convey the blood 
into the vena cava. They are in fact triangu- 
lar veins, running through the substance of the 
dura mater, and, like the processes, are dis- 
tinguished into longitudinal and lateral; and 
where these three meet, and where the fourth 
process passes off, we observe a fourth sinus, 
-which is called toreular ; Herophilus, who first 
described it, having supposed that the blood at 
the union of these two veins, is, as it were, in 
a press. 

Besides these four canals, which were 
known to the ancients, modern anatomists enu- 
merate many others, by giving the appellation 
of sinuses to other veins of the dura mater, 
which for the most part empty themselves into 
some of those we have just now described. 
There are the inferior longitudinal sinus, the 
superior ard inferior petrous sinuses, the ca- 



Of the Brain and Nerves. 369 

vernous sinuses, the circular sinus, and the 
anterior and posterior occipital sinuses. 

These sinuses or veins, by being conveyed 
through a thick dense membrane, firmly sus- 
pended, as the dura mater is, within the cra- 
nium, are less liable to rupture ; at the same 
time they are well supported, and by running 
every where along the inner surface of the 
bones, they are prevented from pressing on the 
substance of the brain. To prevent too great 
a dilatation of them, we find filaments (called 
choreics Willisii, from their having been first 
noticed by Willis) stretched across their cavi- 
ties ; and the oblique manner in which the 
veins from the brain run through the substance 
of the brain into these channels, serves the 
purpose of a valve, which prevents the blood 
from turning back into the smaller and weaker 
vessels of the brain. 

The pia mater is a much softer and finer 
membrane than the dura mater ; being exceed- 
ingly delicate, transparent, and vascular. It in- 
vests every part of the brain, and sends off an 
infinite number of elongations, which insinu- 
ate themselves between the convolutions, and 
even into the substance of the brain. This 
membrane is composed of two laminae ; of which 
the exterior one is named tunica arachnoidea, 
from its thinness, which is equal to that of a 
spider's web. These two laminas are intimate- 
ly adherent to each other at the upper part of 
the brain, but are easily separable at the basis 
of the brain, and through the whole length of 
the medulla spinalis. The external layer, or 
tunica arachnoidea, appears to be spread uni- 

3 A 



3 70 Of the Brain and Nerves. 

formly over the surface of the brain, but with- 
out entering into its furrows as the inner layer 
does ; the latter being found to insinuate itself 
between the convolutions, and even into the 
interior cavities of the brain. The blood-ves- 
sels of the brain are distributed through it in 
their way to that organ, and are therefore di- 
vided into very minute ramifications, before 
they penetrate the substance of the brain. 

There are several parts included under the 
general denomination of brain. One of these, 
which is of the softest consistence, and fills 
the greatest part of the cavity of the cranium, 
is the cerebrum, or brain properly so called. 
Another portion, which is seated in the infe- 
rior and posterior part of the head, is the cere- 
bellum ; and a third, which derives its origin 
from both these, is the medulla oblongata. 

The cerebrum is a medullary mass of a mo- 
derate consistence, filling up exactly all the 
upper part of the cavity of the cranium, and 
divided into two hemispheres by the falx of 
the dura mater. Each of these hemispheres 
is usually distinguished into an interior, a mid- 
dle, and a posterior lobe. The first of these is 
lodged on the orbital processes of the os fron- 
tis : the middle lobes lie on the middle fossse of 
the basis of the cranium, and the posterior 
lobes are placed on the transverse septum of 
the os occipitis, immediately over the cerebel- 
lum, from which they are separated by the la- 
teral processes of the dura mater. These two 
portions afford no distinguishing mark of se- 
paration ; and on this account Haller, and many 
other modern anatomists, omit the distinction 



Of the Brain and Nerves. 371 

of middle lobe, and speak only of the anterior 
and posterior lobes of the bra;n. 

The cerebrum appears to be composed of 
two distinct substances. Of these, the exte- 
rior one, which is of a greyish or ash-colour, 
is called the cortex, and is somewhat softer 
than the other, which is very white, and is call- 
ed medulla or substantia alba. 

After having removed the falx, and separat- 
ed the two hemispheres from each other, we 
perceive a white convex body, the corpus cal- 
losum, which is a portion of the medullary 
substance, uniting the two hemispheres to 
each other, and not invested by the cortex. 
By making an horizontal incision in the brain, 
on a level with this corpus callosum, we dis- 
cover two oblong cavities, named the anterior 
or lateral ventricles, one in each hemisphere. 
r I hese two ventricles, which communicate with 
each other by a hole immediately under the 
plexus choroides, are separated laterally by a 
very fine medullary partition, called septum 
lucidum, from its thinness and transparency. 
The lower edge of this septum is fixed to the 
fornix, which is a kind of medullary arch (as 
its name implies) situated under the corpus 
callosum, and nearly of a triangular shape. 
Anteriorly the fornix sends off two medullary 
chords, called its anterior crura ; which seem 
to be united to each other by a portion of me- 
dullary substance, named commissura anterior 
cerebri. These crura diverging from one ano- 
ther, are lost at the outer side of the lower 
and fore-part of the third ventricle. Posteri- 
orly the fornix is formed into two other crura, 



372 Of the Brain and Nerves. 

which unite with two medullary protuberances 
called pedes hippocampi, and sometimes cornua 
ammonis, that extend along the back part of 
the lateral ventricles. The concave edge of 
the pedes hippocampi is covered by a medul- 
lary lamina, called corpus Jimbriatum. 

Neither the edges ol the fornix, nor its pos- 
terior crura, can be well distinguished, till we 
have removed the plexus choroides. This is 
a production of the pia mater, which is spread 
over the lateral ventricles. Its loose edges 
are collected, so as to appear like a vascular 
band on each side. 

When we have removed this plexus, we dis- 
cover several other protuberances included in 
the lateral ventricles. These are the corpora 
striata, the thalami nervorum opticorum, the 
tubercula quadrumgemina, and the pineal 
gland. 

The corpora striata are two curved oblong 
eminences, that extend along the anterior part 
of the lateral ventricles. They derive their 
name from their striated appearance, which is 
owing to an intermixture of the cortical and 
medullary substances of the brain. The thala- 
mi nervorum opticorum, are so called, because 
the optic nerves arise chiefly from them, and 
they are likewise composed both of the cortex 
and medulla. They are separated from the 
corpora striata only by a kind of medullary 
chord, the geminum centrum semi-circulare. 
The thalami are nearly of an oval shape, and 
are situated at the bottom of the upper cavity 
of the lateral ventricles. They are closely 



Of the Brain and Nerves. 373 

united, and at their convex part seem to be- 
come one body. 

Anteriorly, in the space between the thala- 
mi, we observe an orifice by which the lateral 
ventricles communicate, and another leads 
down from this, under the different appella- 
tions of foramen commune anterius, vulva iter 
ad infundibidum, but more properly iter adter- 
tium ventriculum ; and the separation of the 
thalami from each other posteriorly, forms 
another opening or interstice called anus. This 
has been supposed to communicate with the 
third ventricle ; but it does not, the bottom of 
it being shut up by the pia mater. The back 
part of the anus is formed by a kind of medul- 
lary band, which connects the thalami to each 
other, and is called conunissura posterior ce- 
rebri. 

Behind the thalami and commissura poste- 
rior, we observe a small, soft, greyish, and 
oval body, about the size of a pea. This is 
the glandula pinealis ; it is described by Galen 
under the name of conarion, and has been ren- 
dered famous by Descartes, who supposed it 
to be the seat of the soul. Galen seems for- 
merly to have entertained the same opinion. 
Some modern writers have, with as little rea- 
son, imagined that the soul is placed in the 
corpus callosum. 

The pineal gland rests upon four remarka- 
ble eminences, disposed in pairs, and seated 
immediately below it. These tubercles, which 
by the ancients were called testes and nates, 
have, since the time of Winslow, been more 
commonly named tubercula quadrugemina. 



374 Of the Brain and Nerves* 

Under the thalami we observe another ca- 
vity, the third ventricle, which terminates aiir- 
tenorly in a small medullary canal, the infun- 
<libulum, that leads to the glandula pituitaria. 

It has been doubted, whether the infuncii- 
bulum is really hollow ; but some late experi- 
ments on this part of the brain * by Professor 
Murray of Upsal, clearly prove it to be a me- 
dullary canal, surrounded by both laminae of 
the pia mater. After freezing the brain, this 
channel was found rilled with ice; and de 
Haen tells f us, he found it dilated, and filled 
with a calcareous matter.! 

The soft spongy body in which the infundi- 
bulum terminates, was by the ancients sup- 
posed to be of a glandular structure, and des- 
tined to filter the serosity of the brain. Spi- 
gelius pretended to have discovered its excre- 
tory duct, but it seems certain that no such 
duct exists. It is of an oblong shape, com- 
posed, as it were, of two lobes. In ruminant 
animals it is much larger than in man. 

From the posterior part of the third ventri- 
cle, we see a small groove or channel, de- 
scending obliquely backwards. This channel, 
which is called the aqueduct of Sylvius, though 
it was known to the ancients, opens into ano- 
ther cavity of the brain, placed between the 
cerebellum and medulla oblongata, and called 
the fourth ventricle. 

* Disp. de Infundibulo Cerebri. 

-(• Ratio Med. torn. vi. p. 271. 

4: The under part of it, however, appears to be impervious ; 
at least no injection that can be depended on has been made to 
pass from it into the glandula pituitaria without laceration of 
parts. 



Of the Brain and Nerves. 375 

The cerebellum, which is divided into two 
lobes, is commonly supposed to be of a firmer 
texture than the cerebrum ; but the truth is, 
that in the greater number of subjects, there 
appears to be no sensible difference in the con- 
sistence of these two parts. It has more of the 
cortical than of the medullary substance in its 
composition. 

The furrow that divides the two lobes of 
the cerebellum leads anteriorly to a process, 
composed of medullary and cortical substan- 
ces, covered by the pia mater ; and which, 
from its being divided into numerous furrows,, 
resembling the rings of the earth-worm, is 
named processus vermiformis. This process 
forms a kind of ring in its course between the 
lobes. 

The surface of the cerebellum does not af- 
ford those circumvolutions which appear in the 
cerebrum ; but instead of these, we observe a 
great number of minute furrows, running pa- 
rallel to each other, and nearly in a transverse 
direction. The pia mater insinuates itself into 
these furrows. 

When we cut into the substance of the cere- 
bellum, from above downwards, we find the 
medullary part running in a kind of ramifying- 
course, and exhibiting an appearance that has- 
gotten the name of arbor vitce. These ramifi- 
cations unite to form a medullary trunk ; the 
middle, anterior, and most considerable part 
of which forms two processes, the crura cere- 
belli, which unite with the crura cerebri, to 
form the medulla oblongata. The last furnish- 
es two other processes, which lose themselves 



3 76 Of the Brain and Nerves. 

under the nates, and thus unite the lobes of 
the cerebellum to the posterior part of the ce- 
rebrum. Under the nates we observe a trans- 
verse medullary line, or linea alba, running 
from one of these processes to the other; and 
between them we find a very thin medullary 
lamina, covered with the pia mater, which 
the generality of anatomists have (though 
seemingly without reason) considered as a 
valve formed for closing the communication 
between the fourth ventricle and the aquaeduc- 
tus Sylvii. Vieussens named it valvula ma- 
jor cerebri. 

The medulla oblongata is situated in the mid- 
dle, lower, and posterior part of the cranium, 
and may be considered as a production or con- 
tinuation of the whole medullary substance of 
the cerebrum and cerebellum, being formed 
by the union of two considerable medullary 
processes of the cerebrum, called crura cerebri, 
with two other smaller ones from the cerebel- 
lum, which were just now spoken of under 
the name of crura cerebelli. 

The crura cerebri arise from the middle and 
lower part of each hemisphere. They are se- 
parated from each other at their origin, but are 
united below, where they terminate in a mid- 
dle protuberance, the pons Varolii, so called, 
because Varolius compared it to a bridge. 
This name, however, can convey no idea of its 
real appearance. It is, in fact, nothing more 
than a medullary protuberance, nearly of a se- 
mi-spherical shape, which unites the crura ce- 
rebri to those of the cerebellum. 



Of the Brain and Nerves. 377 

Between the crura cerebri, and near the an- 
terior edge of the pons Varolii, are two tuber- 
cles, composed externally of medullary, and 
internally of cineritious, substance, to which 
Eustachius first gave the name of eminentia 
mamillarcs. 

Along the middle of the posterior surface 
of the medulla oblongata, where it forms the 
anterior part of the fourth ventricle, we observe 
a kind of furrow which runs downwards and 
terminates in a point. About an inch above 
the lower extremity of this fissure, several me- 
dullary filaments are to be seen running to- 
wards it on each side in an oblique direction, 
so as to give it the appearance of a writing- 
pen ; hence it is called calamus scriptorius. 

From the posterior part of the pons Varolii, 
the medulla oblongata descends obliquely back- 
wards ; at its fore-part, immediately behind 
the pons Varolii, we observe two pair of emi- 
nences, which were described by Eustachi- 
us, but received no particular appellation till 
the time of Vieussens, who gave them the 
names of corpora olivaria and corpora pyrami- 
dalia. The former are the outermost, being 
placed one on each side. They are nearly of 
an oval shape, and are composed of medulla, 
with streaks of cortical substance. Between 
these are the corpora pyramidalia, each of 
which terminates in a point. In the human 
subject these four eminences are sometimes 
not easily distinguished. 

The medulla spinalis or spinal marrow^ 
which is the name given to the medullary 
chord that is extended down the vertebral ca- 

3 B 



378 Of the Brain and Nerves. 

nal, from the great foramen of the occipital 
bone to the bottom of the last lumbar vertebra, 
is a continuation of the medulla oblongata. Like 
the other parts of the brain, it is invested by 
the dura and pia mater. The first of these, in 
its passage out of the cranium, adheres to the 
foramen of the os occipitis. Its connection with 
the ligamentary substance that lines the cavity 
of the spine, is only by means of cellular mem- 
brane ; but between the several vertebrae, where 
the nerves pass out of the spine, it sends off 
prolongations, which adhere strongly to the 
vertebral ligaments. Here, as in the cranium, 
the dura mater has its sinuses or large veins. 
These are two in number, and are seen run- 
ning on each side of the medullary column, 
from the foramen magnum of the os occipitis 
to the lower part of the os sacrum. They 
communicate together by ramifying branches 
at each vertebra, and terminate in the verte- 
bral, intercostal, and sacral veins. 

The pia mater is connected with the dura 
mater by means of a thin transparent sub- 
stance which from its indentations between 
the spinal nerves has obtained the name of 
ligamentum denticulatum. It is somewhat firm- 
er than the tunica arachnoidea, but in other re- 
spects resembles that membrane. Its use is 
to support the spinal marrow, that it may not 
affect the medulla oblongata by its weight. 

The spinal marrow itself is externally of a 
white colour ; but upon cutting into it we find 
its middle-part composed of a darker coloured 
mass, resembling the cortex of the brain. When 
the marrow has reached the first lumbar ver- 



Of the Brain and Nerves. 379 

tebra, it becomes extremely narrow, and at 
length terminates in an oblong protuberance ; 
from the extremity of which the pia mater 
sends off a prolongation or ligament, resem- 
bling a nerve, that perforates the dura mater, 
and is fixed to the os coccygis. 

The medulla spinalis gives rise to 30 or 31 
pair of nerves, but they are not all of the same 
size, nor do they all run in the same direc- 
tion. The upper ones are thinner than the 
rest, and are placed almost transversely : as 
we descend we find them running more and 
more obliquely downwards, till at length their 
course is almost perpendicular, so that the low- 
ermost nerves exhibit an appearance that is 
called cauda equina, from its resemblance to a 
horse's tail. 

The arteries that ramify through the differ- 
ent parts of the brain, are derived from the 
internal carotid and from the vertebral arteries. 
The medulla spinalis is supplied by the ante- 
rior and posterior spinal arteries, and likewise 
receives branches, from the cervical, the infe- 
rior and superior intercostal, the lumbar, and 
the sacral arteries. 



Sect. II. Of the Nerves. 

The nerves are medullary chords, differing 
from each other in size, colour, and consist- 
ence, and deriving their origin from the me- 
dulla oblongata and medulla spinalis. There 
are 39, and sometimes 40, pairof these nerves; 



380 Of the Brain and Nerves. 

nine* of which originate from the medulla 
oblongata, and SO or 31 from the medulla spi- 
nalis. Tliey appear to be perfectly inelastic, 
and likewise to possess no irritability. If we 
irritate muscular fibres, they immediately con- 
tract ; but nothing of this sort happens if we 
irritate a nerve. They carry with them a co- 
vering from the pia mater ; but derive no tu- 
nic from the dura mater, as hath been gene- 
rally, though erroneously, supposed, ever since 
the time of Galen,f the outer covering of the 
nerves being in fact nothing more than the cel- 
lular membrane. This covering is very thick 
where the nerve is exposed to the action of 
muscles ; but where it runs through a bony ca- 
nal, or is secure from pressure, the cellular 
tunic is extremely thin, or altogether wanting. 
We have instances of this in the portio mollis 
of the auditory nerve, and in the nerves of the 
heart. 

By elevating, carefully and gently, the brain 
from the basis of the cranium, we find the first 
nine pair arising in the following order: 1. 
The nervi olfactorii, distributed through the 
pituitary membrane, which constitutes the or- 
gan of smell. 2. The optici, which go to the 

* It has been usual to describe the ten pair of nerves as aris- 
ing from the medulla oblongata ; but as the tenth pair arise in 
the fame manner as the other spinal nerves, Santorini, Heister, 
Haller, and others, seem very properly to have classed them 
among the nerves of the spine. 

f Baron Haller and Professor Zinn seem to have been the 
first who demonstrated, that the dura mater is reflected upon 
and adheres to the periosteum at the edges of the foramina that 
afford a passage to th? nerves out of the cranium, and vertebral 
eanal, or is soon lost in the cellular substance. 



Of the Brain and Nerves. 381 

eyes, where they receive the impressions of 
visible objects. 3. The oculorum motores, so 
called because they are distributed to the mus- 
cles of the eye. 4. The pathetici, distributed 
to the superior oblique muscles of the eye, the 
motion of which is expressive of certain passions 
of the soul. 5. The nerves of this pair soon 
divide into three principal branches, and each 
of these has a different name. Its upper di- 
vision is the ophthalmicus, which is distribut- 
ed to various parts of the eyes, eye-lids, fore- 
head, nose, and integuments of the face. The 
second is called the maxillaris superior, and 
the third maxillaris inferior ; both which names 
allude to their distribution. 6. The abducto- 
res ; each of these nerves is distributed to the 
abductor muscle of the eye, so called, because 
it helps to draw the globe of the eye from the 
nose. 7. The auditorii,* which are distribut- 
ed through the organs of hearing. 8. The 
par vagum, which derives its name from the 
great number of parts to which it gives branch- 
es both in the thorax and abdomen. 9. The 
linguales, or hypo-glossi, which are distribut- 
ed to the tongue, and appear to contribute both 
to the organ of taste and to the motions of the 
tongue, f 

* This pair, soon after its entrance into the meatus auditorim 
internus, separates into two branches. One of these is of a very 
soft and pulpy consistence, it is called the portio mollis of the se- 
venth pair, and is spread over the inner part of the ear. The 
other passes out through the aqueduct of Fallopius in a firm 
chord, which is distinguished as the portio dura, and is distribut- 
ed to the external ear and other parts of the neck and face. 

+ Heistcr has summed up the ufes of these nine pair of 
nerves in the two following Latin verses : 



382 Of the Brain and Nerves. 

It has already been observed, that the spi- 
nal marrow sends off 30 or 31 pair of nerves ; 
these are chiefly distributed to the exterior parts 
of the trunk and to the extremities. They are 
commonly distinguished into the cervical, dorsal, 
lumbar, and sacral nerves. The cervical, which 
pass out from between the several vertebrae 
of the neck are eight* in number ; the dorsal, 
twelve ; the lumbar, five ; and the sacral, five 
or six ; the number of the latter depending on 
the number of holes in the os sacrum. Each 
spinal nerve at its origin is composed of two 
fasciculi of medullary fibres. One of these 
fasciculi arises from the anterior, and the other 
from the posterior, surface of the medulla. 
These fasciculi are separated by the ligamen- 
tum denticulatum ; after which we find them 
contiguous to one another. They then perfo- 
rate the dura mater, and unite to form a con- 
siderable knot or ganglion. Each of these 

a Olfaciens, cernens, oculosque movent, paliensque, 

** Gas tans, abclucens, audiensque, vagansqtte, loquensquc ." 

* Besides these, there is another pair called accessorii, which 
arises from the medulla spinalis at its beginning : and ascending 
through the great foramen of the os occipitis into the cranium, 
passes out again close to the eighth pair, with which, however, 
it does not unite ; and it is afterwards distributed chiefly to the 
muscles of the neck, back, and scapula. In this course it sends 
off filaments to different parts, and likewise communicates with 
several other nerves. Physiologists are at a loss how to account 
for the singular origin and course of these nervi accessorii. The 
ancients considered them as branches of the eighth pair, distri- 
buted to muscles of the scapula : Willis likewise considered them 
as appendages to that pair, and on that account named them ac- 
cessor]'. They are sometimes called the spinal pair ; but as this 
latter name is applicable to all the nerves of the spine indiscrimi- 
nately, it seems better to adopt that given by Willis. 



Of the Brain and Nerves. 383 

ganglions sends off two branches ; one ante- 
rior, and the other posterior. The anterior 
branches communicate with each other at their 
coming out of the spine, and likewise send off 
one, and sometimes more branches, to assist 
in the formation of the intercostal nerve. 

The knots or ganglions of the nerves just 
now spoken of, are not only to be met with at 
their exit from the spine, but likewise in vari- 
ous parts of the body. They occur in the 
nerves of the medulla oblongata, as well as in 
those of the spine. They are not the effects 
of disease, but are to be met with in the same 
parts of the same nerves, both in the fcetus 
and adult. They are commonly of an oblong 
shape, and of a greyish colour, somewhat in- 
clined to red, which is perhaps owing to their 
being extremely vascular. Internally we are 
able to distinguish something like an intermix- 
ture of the nervous filaments. 

Some writers have considered them as so 
many little brains ; Lancisi fancied he had dis- 
covered muscular fibres in them, but they are" 
certainly not of an irritable nature. A late 
writer, Dr. Johnstone,* imagines they are in- 
tended to deprive us of the power of the will 
over certain parts, as the heart, for instance: 
but if this hypothesis were well founded, we 
should meet with them only in the nerves lead- 
ing to involuntary muscles ; whereas it is cer- 
tain, that the voluntary muscles receive their 
nerves through ganglions. Doctor Monro, 
from observing the accurate intermixture of the 

* Essay on the Use of the Ganglions of the Nerves. 



384 Of the Brain and Nerves. 

minute nerves which compose them, considers 
them as new sources of nervous energy. f 

The nerves, like the blood-vessels, in their 
course through the body, communicate with 
each other ; and each of these communications 
constitutes what is called a plexus, from whence 
branches are again detached to different parts 
of the body. Some of these are constant and 
considerable enough to be distinguished by 
particular names, as the semilunar plexus ; the 
pulmonary plexus ; the hepatic, the cardiac, &c. 

It would be foreign to the purpose of this 
work, to follow the nerves through all their 
distributions ; but it may be remembered, that in 
describing the different viscera, mention was 
made of the nerves distributed to them. There 
is one pair, however, called the intercostal, or 
great sympathetic nerve, which seems to require 
particular notice, because it has an almost 
universal connection and correspondence with 
all the other nerves of the body. Authors are 
not perfectly agreed about the origin of the 
intercostal ; but it may perhaps not improperly 
be described, as beginning from filaments of the 
fifth and sixth pair; it then passes out of the 
cranium, through the bony canal of the carotid, 
from whence it descends laterally close to the 
bodies of the vertebra?, and receives branches 
from almost all the vertebral nerves ; forming 
almost as many ganglions in its course through 
the thorax and abdomen. It sends off an 
infinite number of branches to the viscera in 

t Observations on the Nervous System. 



Of the Brain and Nerves, 385 

those cavities, and forms several plexuses with 
the branches of the eighth pair or par vagum. 

That the nerves are destined to convey the 
principles of motion and sensibility to the brain 
from all parts of the system, there can be no 
doubt ; but how these effects are produced, no 
one has ever yet been able to determine, The 
inquiry has been a constant source of hypothesis 
in ail ages, and has produced some ingenious 
ideas, and many erroneous positions, but with- 
out having hitherto afforded much satisfactory 
information. 

Some physiologists have considered a trunk 
of nerves as a solid chord, capable of being 
divided into an infinite number of filaments, 
by means of which the impressions of feeling 
are conveyed to the sensorium commune. 
Others have supposed it to be a canal, which 
afterwards separates into more minute channels; 
or, perhaps, as being an assemblage of many 
very small and distinct tubes, connected to 
each other, and thus forming a cylindrical 
chord. They who contend for their being 
solid bodies, are of opinion, that feeling is 
occasioned by vibration : so that, for instance 
according to this system, by pricking the 
finger, a vibration would be occasioned in the 
nerve, distributed through its substance ; and 
the effects of this vibration, when extended to 
the sensorium, would be an excital of pain. 
But the inelasticity, the softness, the con- 
nection, and the situation of the nerves, are 
so many proofs that vibration has no share in 
the cause of feeling. 

3 C 



386 Of the Brain and Nerves. 

Others have supposed, that in the brain and 
spinal marrow, a very subtile fluid is secreted, 
and from thence conveyed through the imper- 
ceptible tubes, which they consider as existing 
in the nerves. They have farther supposed, 
that this very subtiie fluid, to which they have 
given the name of animal spirits, is secreted 
in the cortical substance of the brain and spi- 
nal marrow, from whence it passes through 
the medullary substance. This, like the other 
system, is founded altogether on hypothesis; 
but it seems to be an hypothesis derived Irom 
much more probable principles, and there are 
many ingenious arguments to be brought in 
its supports 



EXPLANATION of PLATE XXIX. 

Fig. 1. Represents the Inferior part of the 
Brain; — the Anterior part of the whole Spine, 
including the Medulla Spinalis ; — with the 
origin and large portions of all the Nerves. 

AA, The anterior lobes of the cerebrum. 
BB, The lateral lobes of the cerebrum. CC, 
The two lobes of the cerebellum. D, Tuber 
annulare. E, The passage from the third 
ventricle to the infundibulum. F, 1 he me- 
dulla oblongata, which sends off the medulla 
spinalis through the spine. G G, That part 
of the os occipitis which is placed above (H H) 
the transverse processes of the first cervical 
vertebra. I I, &c. The seven cervical verte- 




- 



— 



Of the Brain and Nerves. 387 

brae, with their intermediate cartilages. K K, 
&c. The twelve dorsal vertebrae, with their 
intermediate cartilages. L L, &c. The five 
lumbar vertebrae, with their intermediate car- 
tilages. M, The os sacrum- N, The os coc- 
cygis. 

Nerves. — 1 1, The first pair of nerves, nam- 
ed olfactory, which go to the nose. 2 2, The 
second pair, named optic, which goes to form 
the tunica retina of the eye. 3 3, The third 
pair, named motor oculi ; it supplies most of 
the muscles of the eye-ball. 4 4, The fourth 
pair, named pathetic, — which is wholly spent 
upon the musculustrochlearis of the eye. 5 5, 
The fifth pair divides into three branches. — 
The first, named ophthalmic, goes to the orbit, 
supplies the lachrymal gland, and sends 
branches out to the forehead and nose. — 
The second, named superior maxillary, sup- 
plies the teeth of the upper jaw, and some of 
the muscles of the lips. — The third named in- 
ferior maxillary, is spent upon the muscles 
and teeth of the lower jaw, tongue, and mus- 
cles of the lips. 6 6, The sixth pair, which, 
after sending off the beginning of the intercos- 
tal or great sympathetic, is spent upon the ab- 
ductor oculi. 7 7, The seventh pair, named 
auditory, divides into two branches. — The 
largest, named portio mollis, is spent upon the 
internal ear. The smallest, portio dura, joins 
to the fifth pair within the internal ear by a re- 
flected branch from the second of the fifth ; 
and within the tympanum, by a branch from 
the third of the fifth named chorda tympani>—~ 



388 Of the Brain and Nerves. 

Vid. fig. 3. near B. 8 8, &c. The eighth pair, 
named par vagum, — which accompanies the 
intercostal, and is spent upon the tongue, la- 
rynx, pharynx, lungs, and abdominal viscera. 
9 9, The ninth pair, which are spent upon the 
tongue. 10 10, &c. The intercostal, or great 
sympathetic, which is seen from the sixth pair 
to the bottom of the pelvis on each side of the 
spine, and joining with all the nerves of the 
spine ; — in its progress supplying the heart, 
and, with the par vagum, the contents of the 
abdomen and pelvis. 11 11, The accessorius, 
which is spent upon the sternocleido-mastoi- 
dseus and trapezius muscles. 12 12, The first 
cervical nerves; — 13 13, The second cervical 
nerves ; — both spent upon the muscles that lie 
on the neck, and teguments of the neck and 
head. 14 14, The third cervical nerves, which, 
after sending off (15 15, he.) the phrenic 
nerves to the diaphragm, supply the muscles 
and teguments that lie on the side of the neck 
and top of the shoulder. 16 16, The brachial 
plexus, formed by the fourth, fifth, sixth, se- 
venth cervicals, and first dorsal nerves ; which 
supply the muscles and teguments of the su- 
perior extremity. 17 17, The twelve dorsal, 
or proper intercostal nerves, which are spent 
upon the intercostal muscles and some of the 
large muscles which lie upon the thorax. 18 
18, The five lumbar pairs of nerves, which 
supply the lumbar and abdominal muscles, 
and some of the teguments and muscles of the 
inferior extremity. 19 19, The sacro-sciatic, 
or posterior crural nerve, formed by the two 
inferior lumbar, and three superior of the os 



Of the Brain and Nerves. 389 

sacrum. This large nerve supplies the great- 
est part of the muscles and teguments of the 
inferior extremity. 20, The stomachic plexus, 
formed by the eighth pair. 2121, Branches 
of the solar or caehac plexus, formed by the 
eighth pair and intercostals, which supply the 
stomach and chylopoietic viscera. 22 22, 
Branches of the superior and inferior mesen- 
teric plexuses, formed by the eighth pair and 
intercostals, which supply the chylopoietic vis- 
cera, with part of the organs of urine and 
generation. 23 23, Nerves which accompany 
the spermatic cord. 24 24, The hypogastric 
plexus, which supplies the organs of urine 
and generation within the pelvis. 

Fig. 2, 3, 4, 5. Shows different Views of the 
Inferior part of the Brain, cut perpendicu- 
larly through the Middle, — with the Origin 
and large Portions of all the Nerves which 
pass out through the Bones of the Cranium, 
— and the three first Cervicals. 

A, The anterior lobe. B, The lateral lobe 
of the cerebrum. C, One of the lobes of the 
cerebellum. D, Tuber annulare. E, Corpus 
pyramidale, in the middle of the medulla ob- 
longata. F, The corpus olivare, in the side 
of the medulla oblongata. G, The medulla ob- 
longata. H, 1 he medulla spinalis. 

Nerves. — 1 2 3 4 5 6 7 8 and 9, Pairs of 
nerves. 10 10, Nervus accessorius, which 
comes from— 11, 12, and 13, The three first 
cervical nerves. 



390 Of the Senses and their Organs. 



PART VI. OF THE SENSES AND 
THEIR ORGANS. 



IN treating of the senses, we mean to con- 
fine ourselves to the external ones of touch, 
taste, smelling, hearing, and vision. The 
word sense, when applied to these five, seems 
to imply not only the sensation excited in the 
mind by certain impressions made on the body, 
but likewise the organ destined to receive and 
transmit these impressions to the sensorium. 
Each of these organs being of a peculiar struc- 
ture, is susceptible only of particular impres- 
sions, which will be pointed out as we pro- 
ceed to describe each of them separately. 



Sect. I. Of Touch. 

The sense of touch maybe defined to be the 
faculty of distinguishing certain properties of 
bodies by the feel. In a general acceptation, 
this definition might perhaps not improperly 
be extended to every part of the body possess- 
ed of sensibility,"* but it is commonly con- 

* In the course of this article, mention has often been made 
of the sensibility or insensibility of different parts of the body : it 
will therefore, perhaps, not be amiss to observe in this place, 
that many parts which were formerly supposed to possess the 
most exquisite sense, are now known to have but little or no 
feeling, at least in a sound state ; for in an inflamed state, even 
the bones, the most insensible parts of any, become susceptible 



Of the Senses and their Organs. 391 

fined to the nervous papillae of the cutis, or 
true skin, which, with its appendages, and 
their several uses, have been already de- 
scribed. 

I he exterior properties of bodies, such as 
their solidity, moisture, inequality, smooth- 
ness, dryness, or fluidity, and likewise their 
degree of heat, seem all to be capable of mak- 
ing different impressions on the papilla?, and 
consequently of exciting different ideas in the 
sensorium commune. But the organ of touch, 
like all the other senses, is not equally deli- 
cate in every part of the body, or in every 
subject; being in some much more exquisite 
than it is in others. 



Sect. II. Of the Taste. 

The sense of taste is seated chiefly in the 
tongue ; the situation and figure of which are 
sufficiently known. 

On the upper surface of this organ we may 
observe a great number of papillae, which, on 
account of their difference in size and shape, 

of the most painful sensations. This curious discovery is due 
to the late Baron Haller. His experiments prove, that the bones, 
cartilages, ligaments, tendons, epidermis, and membranes (as 
the pleura, pericardium, dura and pia mater, periosteum, .Tee. i 
may in a healthy state be considered as insensible. As sensibuity 
depends on the brain and nerves, of course difFcrent parts will 
possess a greater or less degree of feeling, in proportion as they 
are supplied with a greater or smaller number of nerves. Upon 
this principle it is, that the skin, muscles, stomach, intestines, 
urinary bladder, ureters uterus, vagina peni:, tongue, and re- 
tina, are extremely sensible, while the lungs and glands have 
only an obscure degree of feeling. 



392 Of the Senses and their Organs. 

are commonly divided into three classes. The 
largest are situated towards the basis of the 
tongue. Their number commonly varies from 
seven to nine, and they seem to be mucous 
follicles. Those of the second class are some- 
what smaller, and of a cylindrical shape. They 
are most numerous about the middle of the 
tongue. Those of the third class are very 
minute, and of a conical shape. They are 
very numerous on the apex and edges of the 
tongue, and have been supposed to be formed 
by the extremities of its nerves. 

We observe a line, the linea lingua' mediana, 
running along the middle of the tongue, and 
dividing it as it were into two portions. 1 o- 
wards the basis of the tongue, we meet with 
a little cavity, named by Morgagni foramen 
ccecum, which seems to be nothing more than 
a common termination of some of the excretory 
ducts of mucous glands situated within the 
substance of the tongue. 

We have already observed, that this organ 
is every where covered by the cuticle, which, 
by forming a reduplication, called the frcenum, 
at its under part, serves to prevent the too 
great motion of the tongue, and to fix it in its 
situation. But, besides this attachment, the 
tongue is connected by means of its muscles 
and membranous ligaments, to the lower jaw, 
the os hyoides, and the styloid processes. 

The principal arteries of the tongue are the 
linguales, which arise from the external carotid. 
Its veins empty themselves into the external 
jugulars. Its nerves arise from the fifth, eighth, 
and ninth pair. 



Of the Senses and their Organs. 393 

The variety of tastes seems to be occasioned 
by the different impressions made on the papil- 
lae by the food. The different state of the pa*- 
pillae with respect to their moisture, their figure, 
or their covering, seems to produce a consider- 
able difference in the taste, not only in differ- 
ent people, but in the same subject, in sickness 
and in health. The great use of the taste seems 
to be to enable us to distinguish wholesome and 
salutary food from that which is unhealthy ; and 
we observe that many quadrupeds, by having 
their papillae* very large and long, have the 
faculty of distinguishing flavours with infinite 
accuracy. 



Sect. III. Of Smelling. 

The sense of smelling, like the sense of taste, 
seems intended to direct us to a proper choice 
of aliment, and is chiefly seated in the nose, 
which is distinguished into its external and in- 
ternal parts. The situation and figure of the 
former of these do not seem to require a defini- 
tion. It is composed of bones and cartilages, 
covered by muscular fibres and by the common 
integuments. The bones make up the upper 
portion, and the cartilages the lower one. The 
septum narium, like the nose, is likewise in 
part bony, and in part cartilaginous. These 
bones and their connections were described in 

the osteology. 

3 D 

* Malpighi's description of the papillae, which has been copied 
by many anatomical writers, seems to have been taken chiefly 
from the tongues of heep. 



394 Of the Senses and their Organs. 

The internal part of the nose, besides the 
ossa spongiosa, has six cavities or sinuses, 
the maxillary, the frontal, and the sphenoid, 
which were all described with the bones of the 
head. They all open into the nostrils ; and 
the nose likewise communicates with the 
mouth, larynx, and pharynx, posteriorly be- 
hind the velum palati. 

All these several parts, which are included 
in the internal division of the nose, viz. the in- 
ner surface of the nostrils, the lamellae of the 
ossa spongiosa, and the sinuses, are lined by 
a thick and very vascular membrane, which, 
though not unknown to the ancients, was first 
well described by Schneider,* and is therefore 
now commonly named membrana pituitaria 
Schneideri. This membrane is truly the organ 
of smelling; but its real structure does not yet 
seem to be perfectly understood. It appears 
to be a continuation of the cuticle, which lines 
the inner surface of the mouth. In some parts 
of the nose it is smooth and firm, and in others 
it is loose and spongy. It is constantly moist- 
ened by a mucous secretion ; the finer parts of 
which are carried off by the air we breathe, 
and the remainder, by being retained in the 
sinuses, acquires considerable consistence. 
The manner in which this mucus is secreted 
has not yet been satisfactorily ascertained ; but 
it seems to be by means of mucous follicles. 

Its arteries are branches of the internal max- 
illary and internal carotid. Its veins empty 
themselves into the internal jugulars. The 
first pair of nerves, the olfactory, are spread 

* De Catarrho, lib. iii. 



Of the Senses and their Organs. 395 

over every part of it, and it likewise receives 
branches from the fifth pair. 

After what has been said of the pituitary 
membrane, it will not be difficult to conceive 
how the air we draw in at the nostrils, being 
impregnated with the effluvia of bodies, ex- 
cites in us that kind of sensation we call smell- 
i?ig. As these effluvia, from their being ex- 
ceedingly light and volatile, cannot be capable 
in a small quantity of making any great im- 
pression on the extremities of the olfactory 
nerves, it was necessary to give considerable 
extent to the pituitary membrane, that by this 
means a greater number of odoriferous parti- 
cles might be admitted at the same time. When 
we wish to take in much of the effluvia of any 
thing, we naturally close the mouth, that all 
the air we inspire may pass through the nos- 
trils ; and at the same time, by means of the 
muscles of the nose, the nostrils are dilated, 
and a greater quantity of air is drawn into 
them. 

In many quadrupeds, the sense of smelling 
is much more extensive and delicate than it is 
in the human subject ; and in the human sub- 
ject it seems to be more perfect the -less it is 
vitiated by a variety of smells. It is not al- 
ways in the same state of perfection, being na- 
turally affected by every change of the pitui- 
tary membrane, and of the lymph with whiclj 
that membrane is moistened. 



■3 96 Of the Senses and their Organs. 



Sect- IV. Of Hearing. 

Before we undertake to explain the man- 
ner in which we are enabled to receive the im- 
pressions of sound, it will be necessary to de- 
scribe the ear, which is the organ of hearing. 
It is commonly distinguished into external and 
internal. The former of these divisions in- 
cludes all that we are able to discover without 
dissection, and the meatus auditorius, as far 
as the tympanum ; and the latter, all the other 
parts of the ear. 

The external ear is a cartilaginous funnel, 
covered by the common integuments, and at- 
tached, by means of its ligaments and muscles, 
to the temporal bone. Although capable only 
of a very obscure motion, it is found to have 
several muscles. Different parts of it are dis- 
tinguished by several names ; all its cartila- 
ginous part is called ala or wing, to distin- 
guish it from the soft and pendent part below, 
called the lobe. Its outer circle or border is 
called helix, and the semicircle within this, 
antihelix. The moveable cartilage placed im- 
mediately before the meatus auditorius, which 
it may be made to close exactly, is named 
tragus; and an eminence opposite to this at 
the extremity of the antihelix, is called anti- 
tragus. The concha is a considerable cavity 
formed by the extremities of the helix and an- 
tihelix. The meatus auditorius, which at its 
opening is cartilaginous, is lined with a very 
thin membrane, which is a continuation of the 
cuticle from the surface of the ear. 



Of the Senses and their Organs. 397 

In this canal we find a yellow wax, which 
is secreted by a number of minute glands or 
follicles, each of which has an excretory duct. 
This secretion, which is at first of an oily con- 
sistence, defends the membrane of the tym- 
panum from the injuries of the air ; and by its 
bitterness, prevents minute insects from enter- 
ing into the ear. But when from neglect or 
disease it accumulates in too great a quantity, 
it sometimes occasions deafness. The inner 
extremity of the meatus is closed by a very 
thin transparent membrane, the membrana 
tympani, which is set in a bony circle like the 
head of a drum. In the last century Rivinus, 
professor at Liepsic, fancied he had discovered 
a hole in this membrane, surrounded by a 
sphincter, and affording a passage to the air, 
between the external and internal ear. Cow- 
per, Heister, and some other anatomists, have 
admitted this supposed foramen, which cer- 
tainly does not exist. Whenever there is any 
opening in the membrana tympani, it may be 
considered as accidental. Under the mem- 
brana tympani runs a branch of the fifth pair 
of nerves, called chorda tympani; and beyond 
this membrane is the cavity of the tympanum, 
which is about seven or eight lines wide, and 
half so many in depth ; it is semispherical, and 
every where lined by a very fine membrane. 
There are four openings to be observed in this 
cavity. It communicates with the mouth by 
means of the Eustachian tube. This canal, 
which is in part bony and in part cartilaginous, 
begins by a very narrow opening at the anteri- 
or and almost superior part of the tympanum. 






398 Of the Senses and their Organs. 

increasing in size as it advances towards the 
palate of the mouth, where it terminates by 
an oval opening. This tube is every where 
lined by the same membrane that covers the 
inside of the mouth. The real use of this ca- 
nal does not seem to have been hitherto satis- 
factorily ascertained ; but sound would seem 
to be conveyed through it to the membrana 
tympani, deaf persons being often observed 
to listen attentively with their mouths open. 
Opposite to this is a minute passage, which 
leads to the sinuosities of the mastoid process ; 
and the two other openings, which are in the 
internal process of the os petrosum, are the 
fenestra ovalis, and fenestra rotunda, both of 
which are covered by a very fine membrane. 

There are three distinct bones in the cavity 
of the tympanum ; and these are the malleus, 
incus, and stapes. Besides these there is a 
fourth, which is the os orbiculare, considered 
by some anatomists as a process of the stapes, 
which is necessarily broken off by the violence 
we are obliged to use in getting at these 
bones ; but when accurately considered, it 
seems to be a distinct bone. 

The malleus is supposed to resemble a ham- 
mer, being larger at one extremity, which is 
its head, than it is at the other, which is its 
handle. The latter is attached to the mem- 
brana tympani, and the head of the bone is 
articulated with the incus. 

The incus, as it is called from its shape, 
though it seems to have less resemblance to 
an anvil than to one of the dentes molares with 
its roots widely separated from each other, is 



Of the Senses and their Organs. 399 

distinguished into its body and its legs. One 
of its legs is placed at the entry of the canal 
which leads to the mastoid process ; and the 
other, which is somewhat longer, is articulat- 
ed with the stapes, or rather with the os orbi- 
culare, which is placed between them. 

The third bone is very properly named 
stapes, being perfectly shaped like a stirrup. 
Its basis is fixed into the fenestra ovalis, and 
its upper part is articulated with the os orbicu- 
lare. What is called the fenestra rotunda, 
though perhaps improperly, as it is more oval 
than round, is observed a little above the 
other, in an eminence formed by the os petro- 
sum, and is closed by a continuation of the 
membrane that lines the inner surface of the 
tympanum. The stapes and malleus are each 
of them furnished with a little muscle, the sta- 
pedeus and tensor tympani. The first of these, 
which is the smallest in the body, arises from 
a little cavern in the posterior and upper part 
of the cavity of the tympanum ; and its tendon, 
after passing through a hole in the same ca- 
vern, is inserted at the back part of the head 
of the stapes. This muscle, by drawing the 
stapes obliquely upwards, assists in stretch- 
ing the membrana tympani. 

The tensor tympani,* or internus mallei, as 
it is called by some writers, arises from the 
cartilaginous extremity of the Eustachian tube, 
and is inserted into the back part of the handle 

* Some anatomists describe three muscles of the malleus ; but 
only this one seems to deserve the name of muscle ; what are 
called the externus and obllquus mallei, seeming to be ligaments 
rather than muscles. 



400 Of the Senses and their Organs. 

of the malleus, which it serves to pull inwards, 
and of course helps to stretch the membrana 
tympani. 

The labyrinth is the only part of the ear 
which remains to be described. It is situated 
in the os petrosum, and is separated from the 
tympanum by a partition which is every where 
bony, except at the two fenestra?. It is com- 
posed of three parts ; and these are the vesti- 
bulum, the semicircular canals, and the coch- 
lea. 

The vestibulum is an irregular cavity, much 
smaller than the tympanum, situated nearly in 
the centre of the os petrosum, between the 
tympanum, the cochlea, and the semicircular 
canals. It is open on the side of the tympa- 
num by means of the fenestra ovalis, and com- 
municates with the upper portion of the coch- 
lea by an oblong foramen, which is under the 
fenestra ovalis, from which it is separated only 
by a very thin partition. 

Each of the three semicircular canals forms 
about half a circle of nearly a line in diameter, 
and running each in a different direction, they 
are distinguished into vertical, oblique, and ho- 
rizontal. These three canals open by both 
their extremities into the vestibulum ; but the 
vertical and the oblique being united together 
at one of their extremities, there are only five 
orifices to be seen in the vestibulum. 

The cochlea is a canal which takes a spiral 
course, not unlike the shell of a snail. From 
its basis to its apex it makes two turns and a 
half; and is divided into two canals by a very 
thin lamina or septum, which is in part bony 



Of the Senses and their Organs. 401 

and in part membranous, in such a manner 
that these two canals only communicate with 
each other at the point. One of them opens 
into the vestibulum, and the other is covered 
by the membrane that closes the fenestra ro- 
tunda. The bony lamella which separates the 
two canals is exceedingly thin, and fills about 
two-thirds of the diameter of the canal. The 
rest of the septum is composed of a most deli- 
cate membrane, which lines the whole inner 
surface of the cochlea, and seems to form this 
division in the same manner as the two mem- 
branous bags of the pleura, by being applied 
to each other, form the mediastinum. 

Every part of the labyrinth is furnished with 
a very delicate periosteum, and filled with a 
watery fluid, secreted as in other cavities. This 
fluid transmits to the nerves the vibrations it 
receives from the membrane closing the fenes- 
tra rotunda, and from the basis of the stapes, 
where it rests on the fenestrum ovale. When 
this fluid is collected in too great a quantity, 
or is compressed by the stapes, it is supposed 
to escape through two minute canals or aque- 
ducts, lately described by Dr. Cotunni,* an in- 
genious physician at Naples. One of these 
aqueducts opens into the bottom of the ves- 
tibulum, and the other into the cochlea, near 
the fenestra rotunda. They both pass through 
the os petrosum, and communicate with the ca- 
vity of the cranium where the fluid that passes 
through them is absorbed ; and they are lined 

3 E 

* De aquseductibus Auris Humana: Interna, 8vo, 1760, 



402 Of the Senses and their Organs, 

by a membrane which is supposed to be a pro- 
duction of the dura mater. 

The artei>s of the external ear come from 
the temporal and other branches of the exter- 
nal carotid, and its veins pass into the jugular. 
The internal ear receives branches of arteries 
from the basilary and carotids, and its veins 
empty themselves into the sinuses of the dura 
mater, and into the internal jugular. 

The portio mollis of the seventh pair is dis- 
tributed through the cochlea, the vestibulum, 
and the semi-circular canals ; and the portio 
dura sends off a branch to the tympanum, and 
other branches to the external ear and parts 
near it. 

The sense of hearing, in producing which 
all the parts we have described assist, is occa- 
sioned by a certain modulation of the air col- 
lected by the funnel-like shape of the external 
ear, and conveyed through the meatus audito- 
rius to the membrana tympani. That sound 
is propagated by means of the air, is very ea- 
sily proved by ringing a bell under the receiv- 
er of an air-pump ; the sound it affords being 
found to diminish gradually as the air becomes 
exhausted, till at length it ceases to be heard 
at all. Sound moves through the air with in- 
finite velocity ; but the degree of its motion 
seems to depend on the state of the air, as it 
constantly moves faster in a dense and dry, 
than it does in a moist and rarefied air. 

That the air vibrating on the membrana 
tympani communicates its vibration to the dif- 
ferent parts of the labyrinth, and by means of 



Of the Senses and their Organs. 403 

the fluid contained in this cavity affects the au- 
ditory nerve so as to produce sound, seems to 
be very probable ; but the situation, the mi- 
nuteness, and the variety of the parts which 
compose the ear, do not permit much to be ad- 
vanced with certainty concerning their mode of 
action. 

Some of these parts seem to constitute the 
immediate organ of hearing, and these are all 
the parts of the vestibulum: but there are others 
which seem intended for the perfection of this 
sense, without being absolutely essential to it. 
It has happened, for instance, that the mem- 
brana tympani, and the little bones of the ear, 
have been destroyed by disease, without de- 
priving the patient of the sense of hearing..* 

Sound is more or less loud in proportion to 
the strength of the vibration ; and the variety 
of sounds seems to depend on the difference 
of this vibration ; for the more quick and fre- 
quent it is., the more acute will be the sound, 
and vice versa. 

Before we conclude this article, it will be 
right to explain certain phenomena, which will 
be found to have a relation to the organ of 
hearing. 

Every body has, in consequence of particu- 
lar sounds, occasionally felt that disagreeable 
sensation which is usually called setting the 
teeth on edge: and the cause of this sensation 

* This observation has led to a supposition, that a perforation 
of this membrane may in some cases of deafness be useful ; and 
Mr. Cheselden relates, that, some years ago, a malefactor was 
pardoned on condition that he should submit to this operation ; 
but the public clamour raised against it was so great, that it was 
thought right not to perform it. 



404 Of the Senses and their Organs. 

may be traced to the communication which the 
portio dura of the auditory nerve has with the 
branches of the fifth pair that are distributed 
to the teeth, being probably occasioned by the 
violent tremor produced in the membrana tym- 
pani by these very acute sounds. Upon the 
same principle we may explain the strong idea 
of sound which a person has who holds a vi- 
brating string between his teeth. 

The humming which is sometimes perceiv- 
ed in the ear, without any exterior cause, may 
be occasioned either by an increased action of 
the arteries in the ears, or by convulsive con- 
tractions of the muscles of the malleus and 
stapes, affecting the auditory nerve in such a 
manner as to produce the idea of sound. An 
ingenious philosophical writer* has lately dis- 
covered that there are sounds liable to be ex- 
cited in the ear by irritation, and without any 
assistance from the vibrations of the air. 



Sect. V. Of Vision. 

The eyes, which constitute the organ of vi- 
sion, are situated in two bony cavities named 
orbits, where they are surrounded by several 
parts, which are either intended to protect 
them from external injury, or to assist in their 
motion. 

The globe of the eye is immediately covered 
by two eye-lids or palpebral, which are com- 

* Elliot's Philosophical Observations on the Senses of Vision 
and Hearing, 8vo. 



Of the Senses and their Organs. 405 

posed of muscular fibres covered by the com- 
mon integuments, and lined by a very fine and 
smooth membrane, which is from thence ex- 
tended over part of the globe of the eye, and 
is called tunica conjunctiva. Each eye-lid is 
cartilaginous at its edge ; and this border which 
is called tarsus, is furnished with a row of hairs 
named cilia or eye-lashes. 

The cilia serve to protect the eye from in- 
sects and minute bodies floating in the air, and 
likewise to moderate the action of the rays of 
light in their passage to the retina. At the 
roots of these hairs there are sebaceous folli- 
cles, first noticed by Meibomius, which dis- 
charge a glutinous liniment. Sometimes the 
fluid they secrete has too much viscidity, and 
the eye-lids become glued to each other. 

The upper border of the orbit is covered by 
the eye-brows or supercilia, which by means 
of their two muscles are capable of being 
brought towards each other, or of being carried 
upwards. They have been considered as serv- 
ing to protect the eyes, but they are probably 
intended more for ornament than utility.* 

The orbits in which the eyes are placed, are 
furnished with a good deal of fat, which af- 
fords a soft bed on which the eye performs its 
several motions. The inner angle of each or- 
bit, or that part of it which is near the nose, is 
called canthus major, or the great angle ; and 
the outer angle, which is on the opposite side 
of the eye, is the canthus minor, or little angle. 

* It is observable, that the eyebrows are peculiar to the hu- 
man species. 



406 Of the Senses and their Organs, 

The little reddish body which we observe 
in the great angle of the eye-lids, and which is 
called caruncula lachrymalis, is supposed to be 
of a glandular structure, and, like the follicles 
of the eye-lids, to secrete an oily humour. But 
its structure and use do not seem to have been 
hitherto accurately determined. The surface 
of the eye is constantly moistened by a very 
fine limpid fluid called the tears, which is chief- 
ly, and perhaps wholly, derived from a large 
gland of the conglomerate kind, situated in a 
small depression of the os frontis near the out- 
er angle of the eye. Its excretory ducts pierce 
the tunica conjunctiva just above the cartila- 
ginous borders of the upper eye-lids. When 
the tears were supposed to be secreted by the 
caruncule, this gland was called glandula inno- 
minata ; but now that its structure and uses 
are ascertained, it very properly has the name 
of glandula lachrymalis. The tears poured 
out by the ducts of this gland are, in a natur- 
al and healthy state, incessantly spread over the 
surface of the eye, to keep it clear and trans- 
parent, by means of the eye-lids, and as con- 
stantly pass out at the opposite corner of the 
eye or inner angle, through two minute orifi- 
ces, the puncta lachrymalia ;* being determined 
into these little openings by a reduplication of 
the tunica conjunctiva, shaped like a crescent 
the two points of which answer to the puncta. 

* It sometimes happens, that this very pellucid fluid, which 
moistens the eye, being poured out through the excretory ducts 
of the lachrymal gland faster than it can be carried off through 
the puncta, trickles down the cheek, and is then strictly and pro- 
perly called tears. 



Of the Senses and their Organs. 407 

This reduplication is named membrana, or val- 
vula semilunaris. Each of these puncta is the 
beginning of a small excretory tube, through 
which the tears pass into a little pouch or re- 
servoir, the sacculus lachrymalis, which lies 
in an excavation formed partly by the nasal 
process of the os maxillare superius, and part- 
ly by the os unguis. The lower part of this 
sac forms a duct called the ductus ad nares, 
which is continued through a bony channel, 
and opens into the nose, through which the 
tears are occasionally discharged.* 

The motions of the eye are performed by 
six muscles ; lour of which are straight and 
two oblique. The straight muscles are dis- 
tinguished by the names of elevator, depres- 
sor, adductor, and abductor, from their se- 
veral uses in elevating and depressing the eye, 
drawing it towards the nose, or carrying it 
from the nose towards the temple. x\ll these 
four muscles arise from the bottom of the or- 
bit, and are inserted by flat tendons into the 
globe of the eye. The oblique muscles are 
intended for the more compound motions of the 
eye. The first of these muscles, the obli- 
quus superior, does not, like the other four mus- 
cles we have described, arise from the bottom 
of the orbit, but from the edge of the fora- 
men that transmits the optic nerve, which se- 
parates the origin of this muscle from that of 

* When the ductus ad nares becomes obstructed in conse- 
quence of disease, the tears are no longer able to pass into the nos- 
trils ; the sacculus lachrymalis becomes distended ; and inflam- 
mation, and sometimes ulceration taking place, constitute the 
disease called Jistula lachrymalis. 



408 Of the Senses mid their Organs. 

the others. From this beginning it passes in 
a straight line towards a very small cartilagin- 
ous ring, the situation of which is marked in 
the skeleton by a little hollow in the internal 
orbitar process of the os frontis. The tendon 
of the muscle after passing through this ring, 
is inserted into the upper part of the globe of 
the eye, which it serves to draw forwards, at 
the same time turning the pupil downwards. 

The obliquus inferior arises from the edge 
of the orbit, under the opening of the ductus 
lachrymalis ; and is inserted somewhat poste- 
riorly into the outer side of the globe, serving 
to draw the eye forwards and turn the pupil 
upwards. When either of these two muscles 
acts separately, the eye is moved on its axis ; 
but when they act together, it is compressed 
both above and below. The eye itself, which 
is now to be described, with its tunics, hu- 
mours, and component parts, is nearly of a 
spherical figure. Of its tunics, the conjuncti- 
va has been already described as a partial co- 
vering, reflected from the inner surface of the 
eye-lids over the anterior portion of the eye. 
What has been named albuginea cannot pro- 
perly be considered as a coat of the eye, being 
in fact nothing more than the tendons of the 
straight muscles spread over some parts of the 
sclerotica. 

The immediate tunics of the eye, which are 
to be demonstrated when its partial coverings, 
and all the other parts with which it is sur- 
rounded, are removed, are the sclerotica, cor- 
nea, choroides, and retina. 



Of the Senses and their Organs. 400 

The sclerotica, which is the exterior coat, 
is every where white and opaque* and is join- 
ed at its anterior edge to another, which has 
more convexity than any other part of the 
globe, and being exceedingly transparent is 
called cornea.* These two parts are perfectly 
different in their structure ; so that some ana- 
tomists suppose them to be as distinct from 
each other as the glass of a watch is from the 
case into which it is fixed. The sclerotica is 
of a compact fibrous structure ; the cornea, on 
the other hand, is composed of a great num- 
ber of laminae united by cellular membrane. 
By macerating them in boiling water, they do 
not separate from each other, as some writers 
have asserted ; but the cornea soon softens, 
and becomes of a glutinous consistence. 

The ancients supposed the sclerotica to be a 
continuation of the dura mater. Morgagni, and 
some other modern writers, are of the same 
opinion ; but this point is disputed by Winslow, 
Haller, Zin, and others. The truth seems to 
be, that the sclerotica, though not a production 
of the dura mater, adheres intimately to that 
membrane. 

The choroides is so called because it is fur- 
nished with a great number of vessels. It has 
likewise been named uvea*, on account of its re- 
semblance to a grape. Many modern anatomi- 
cal writers have considered it as a production 
of the pia mater. This was likewise the opinion 

3 F 



* Some writers, who have given the name of cornea to all this 
outer coat, have named what is here and most commonly called 
sclerotica', cornea opaca ; and its anterior and transparent portion, 
cornea lucida. 



410 Of the Senses and their Organs. 

of the ancients ; but the strength and thickness 
of the choroides, when compared with the deli- 
cate structure of the pia mater, are sufficient 
proofs of their being two distinct membranes. 

The choroides has of late generally been de- 
scribed as consisting of two laminae ; the inner- 
most of which has been named after Ruysch, 
who first described it. It is certain, however, 
that Ruysch's distinction is ill founded, at least 
with respect to the human eye, in which we are 
unable to demonstrate any such structure, al- 
though the tunica choroides of sheep and some 
other quadrupeds may easily be separated into 
two layers. 

The choroides adheres intimately to the scle- 
rotica round the edge of the cornea ; and at the 
place of this union, we may observe a little 
whitish areola, named ligamentum ciliare 9 
though it is not of a ligamentous nature. 

They who suppose the choroides to be com- 
posed of two laminse, describe the external one 
as terminating in the ligamentum ciliare, and 
the internal one as extending farther to form the 
iris, which is the circle we are able to distin- 
guish through the cornea ; but this part is of a 
very different structure from the choroides ; 
so that some late writers have perhaps not im- 
properly considered the iris as a distinct mem- 
brane. It derives its name from the variety of 
its colours, and is perforated in the middle. — 
This perforation, which is called the pupil or 
sight of the eye, is closed in the foetus by a very 
thin vascular membrane. This membrana pu- 
pillaris commonly disappears about the seventh 
month. 



Of the Senses and their Organs. 411 

On the under side of the iris we observe ma- 
ny minute fibres, called ciliary processes, which 
pass in radii or parallel lines from the circum- 
ference to the centre. The contraction and 
dilatation of the pupil are supposed to depend 
on the action of these processes. Some have 
considered them as muscular, but they are 
not of an irritable nature : others have sup- 
posed them to be filaments of nerves ; hut 
their real structure has never yet been clearly 
ascertained. 

Besides these ciliary processes, anatomists 
usually speak of the circular fibres of the iris, 
but no such seem to exist. 

The posterior surface of the iris, the ciliary 
processes, and part of the tunica choroides, 
are covered by a black mucus for the purposes 
of accurate and distinct vision ; but the man- 
ner in which it is secreted has not been deter- 
mined. 

Immediately under the tunica choroides we 
find the third and inner coat, called the retina, 
which seems to be merely an expansion of the 
pulpy substance of the optic nerve, extending 
to the border of the crystalline humour. 

The greatest part of the globe of the eye, 
within these several tunics, is filled by a very 
transparent and gelatinous humour of conside- 
rable consistence, which, from its supposed 
resemblance to fused glass, is called the vitre- 
ous humour. It is invested by a very fine and 
delicate membrane, called tunica vitrea, and 
sometimes arachnoides.—rlt is supposed to be 
composed of two laminae ; one of which dips 
into its substance, and by dividing the hu- 



412 Of the Senses and their Organs, 

mour into cells adds to its firmness. The 
fore-part of the vitreous humour is a little, 
hollowed, to receive a very white and trans- 
parent substance of a firm texture, and of a 
lenticular and somewhat convex shape, named 
the crystalline humour. It is included in a 
capsula, which seems to be formed by a sepa- 
ration of the two laminse of the tunica vitrea. 

The fore-part of the eye is filled by a very 
thin arid transparent fluid, named the aqueous 
humour, which occupies all the space between 
the crystalline and the prominent cornea — 
The part of the choroides which is called the 
iris, and which comes forward to form the 
pupil, appears to be suspended as it were in 
this humour, and has occasioned this portion 
of the eye to be distinguished into two parts. 
One of these, which is the little space between 
the anterior surface of the crystalline and the 
iris, is called the posterior chamber ; and the 
other, which is the space between the iris and 
the cornea, is called the anterior chamber of 
the eye.* Both these spaces are completely 
filled with the aqueous humour.f 

* We are aware that some anatomists, particularly Lieutaud, 
are of opinion, that the iris is every where in close contact with 
the crystalline, and that it is of course right to speak only of one 
chamber of the eye ; but as this does not appear to be the case, 
the situation cf the iris and the two chambers of the eye are here 
described in the usual way. 

f When the crystalline becomes opaque, so as to prevent the 
passage of the rays of light to the retina, it constitutes what is 
called a cataract ; and the operation of couching consists in re- 
moving the diseased crystalline from its bed in the vitreous hu- 
mour. In this operation the cornea is perforated, and the aque- 
ous humour escapes out of the eye, but it is constantly renewed 
again in a very short time. The manner, however, in which it 
is secreted, has not yet been determined. 



Of the Senses ar,d their Organs. 413 

The eye receives its arteries from the in- 
ternal carotid through the foramina optica ; 
and its veins pass through the foramina lacera, 
and empty themselves into the lateral sinuses. 
Some of the ramifications of these vessels ap- 
pear on the inner surface of the iris, where 
they are seen to make very minute convolu- 
tions, which are sufficiently remarkable to be 
distinguished by the name of circulus arteriosus^ 
though perhaps improperly, as they are chief- 
ly branches of veins. 

The optic nerve passes in at the posterior 
part of the eye, in a considerable trunk, to be 
expanded for the purposes of vision, of which 
it is now universally supposed to be the im- 
mediate seat. But Messrs. Mariotte and Mery 
contended, that the choroides is the seat of 
this sense ; and the ancients supposed the 
crystalline to be so. Besides the optic, the 
eye receives branches from the third, fourth, 
fifth, and sixth pair of nerves. 

The humours of the eye, together with the 
cornea, are calculated to refract and converge 
the rays of light in such a manner as to form 
at the bottom of the eye a distinct image of the 
object we look at; and the point where these 
rays meet is called the focus of the eye. On 
the retina, as in the camera obscura, the ob- 
ject is painted in an inverted position ; and it 
is only by habit that we are enabled to judge 
of its true situation, and likewise of its dis- 
tance and magnitude. To a young gentleman 
who was born blind, and who was couched by 
Mr. Cheselden, every object (as he expressed 
himself) seemed to touch his eyes as what he 



A14, Of the Senses and their Organs. 

felt did his skin ; and he thought no objects so 
agreeable as those which were smooth and 
regular, although for some time he could form 
no judgment of their shape, or guess what it 
was in any of them that was pleasing to him. 

In order to paint objects distinctly on the 
retina, the cornea is required to have such a 
degree of convexity, that the rays of light may 
be collected at a certain point, so as to termi- 
nate exactly on the retina. — If the cornea is 
too prominent, the rays, by diverging too soon, 
will be united before they reach the retina, 
as is the case with near-sighted people or 
myopes ; and on the contrary, if it is not suf- 
ficiently convex, the rays will not be perfectly 
united when they reach the back part of the 
eye ; and this happens to long-sighted people 
or presbi, being found constantly to take place 
as we approach to old age, when the eye gra- 
dually flattens.* These defects are to be sup- 
plied by means of glasses. He who has too 
prominent an eye, will find his vision improv- 
ed by means of a concave glass ; and upon 
the same principles, a convex glass will be 
found useful to a person whose eye is natu- 
rally too flat. 



* Upon this principle, they who in their youth are near sight- 
ed may expect to see better as they advance in life, as their eyes 
gradually become more flat. 




* 



Of the Senses and their Organs. 415 



EXPLANATION OF PLATE XXX. 



Figure 1. Shows the Lachrymal Canals, 
after the Common Teguments and Bones 
have been cut away. 

a, The lachrymal gland, b, The two punc- 
ta lachrymalia, from which the two lachry- 
mal canals proceed to c, The lachrymal sac. 
d, The large lachrymal duct, e, Its opening 
into the nose, f, The caruncula lachrymalis. 
g, The eye-ball. 

Fig. 2. An interior View of the Coats and 
Humours of the Eye. 

a a a a, The tunica sclerotica cut in four 
angles, and turned back, b b b b, The tunica 
choroides adhering to the inside of the sclero- 
tica, and the ciliary vessels are seen passing 
over — c c, The retina which covers the vitre- 
ous humour. d d, The ciliary processes, 
which were continued from the choroid coat. 
© e, The iris, f, The pupil. 

Fig. 3. Shows the Optic Nerves, and Mus- 
cles of the Eye. 

a a, The two optic nerves before they meet, 
bf The two optic nerves conjoined, c, The 



416 Of the Senses and their Organs. 

right optic nerve, d, Musculus attollens pal- 
pebral superioris. e, Attollens oculi. f, Ab- 
ductor, g g, Obliquus superior, or trochle- 
ars, h, Adductor, i, The eye-ball. 

Fig. 4. Shows the Eye-ball with its Muscles. 

a, The optic nerve, b, Musculus trochle- 
ars, c, Part of the os frontis, to which the 
trochlea or pully is fixed, through which, — d, 
The tendons of the trochlearis passes, e, At- 
tollens oculi. f, Adductor oculi. g, Abduc- 
tor oculi. h, Obliquus inferior, i, Part of the 
superior maxillary bone to which it is fixed. k, 
The eye-ball. 

Fig. 5. Represents the Nerves and Muscles 
of the Right Eye, after part of the Bones of 
the orbit have been cut away. 

A, The eye-ball. B, The lachrymal gland. 
C, Musculus abductor oculi. D, Attollens. 
E, Levator palpebree superioris. F, Depres- 
sor oculi. G, Adductor. H, Obliquus superi- 
or, with its pully. I, Its insertion into the 
sclerotic coat. K, Part of the obliquus inferior. 
L, The anterior part of the os frontis cut. M, 
The crista galli of the ethmoid bone. N, The 
posterior part of the sphenoid bone. O, Trans- 
verse spinous process of the sphenoid bone. 
P, The carotid artery, denuded where it pass- 
es through the bones. Q, The carotid artery 
within the cranium. R, The ocular artery. 



Of the Senses and their Organs. 417 

Nerves. — a a, The optic nerve, b, The 
third pair. — c, Its joining with a branch of the 
first branch of the fifth pair, to form 1, — The 
lenticular ganglion, which sends off the ciliary- 
nerves, d. ee, The fourth pair, f, The trunk 
of the fifth pair, g, The first branch of the 
fifth pair, named ophthalmic. — h, The frontal 
branch of it. i, Its ciliary branches, along 
with which the nasal twig is sent to the nose, 
k, Its branch to the lachrymal gland. 1, 
The lenticular ganglion. m, The second 
branch of the fifth pair, named superior max- 
illary, n, The third branch of the fifth pair, 
named inferior maxillary, o, The sixth pair 
of nerves, — which sends off p, The beginning 
of the great sympathetic, q, The remainder of 
the sixth pair, spent on c, The abductor oculi. 

Fig. 6. Represents the head of a youth, where 
the upper part of the cranium is sawed off, — 
to show the upper part of the brain, covered 
by the pia mater, the vessels of which are 
minutely filled with wax. 

A A, The cut edges of the upper part of 
the cranium. B, The two tables and interme- 
diate diploe. B B, The two hemispheres of 
the cerebrum. C C, The incisure made by 
the falx. D, Part of the tentorium cerebello 
super expansum. E, Part of the falx, which 
is fixed to the crista galli. 

3 G 



418 Of the Senses and their Organs. 

Fig. 7. Represents the parts of the External 
Ear, with the Parotid Gland and its Duct. 

a a, The helix, b, The antihelix. c, The 
antitragus. d, The tragus. e, The lobe of 
the ear. f, The cavitas innominata. g, The 
scapha. h, The concha. i i, The parotid 
gland, k, A lymphatic gland, which is often 
found before the tragus. 1, The duct of the 
parotid gland, m, Its opening into the mouth. 

Fig. 8. A view of the posterior part of the 
external ear, meatus auditorius, tympanum, 
with the small bones, and Eustachian tube 
of the right side. 

a, The back part of the meatus, with the 
small ceruminous glands, b, The incus, c, 
Malleus, d, The chorda tympani. e, Mem-i 
brana tympani. f, The Eustachian tube, g, 
Its mouth from the fauces. 



Fig. 9. Represents the anterior part of the 
right external ear, the cavity of the tympa- 
num—its small bones, cochlea, and semicir- 
cular canals. 

a, The malleus, b, Incus with its long leg, 
resting upon the stapes, c, Membrana tym- 
pani. d, e, The Eustachian tube, covered by 
part of — f f, The musculus circumflexus palati. 
1, 2, 3, The three semicircular canals. 4, 
The vestible. 5, The cochlea. 6, The por- 
tio mollis of the seventh pair of nerves. 



Of the Senses and their Organs. 419 

Fig. 10. Shows the muscles which compose 
the fleshy substance of the Tongue. 

a a, The tip of the tongue, with some of the 
papillae minimae. b, The root of the tongue. 
c, Part of the membrane of the tongue, which 
covered the epiglottis. d d, Part of the mus- 
culus hyo-glossus. e, The lingualis. f, Ge- 
nio-glossus. g g, Part of the stylo-glossus. 



THE END. 



MexL Hist. 
WZ 

If 65